Natural Sciences and Technology - Grade 6 CAPS

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Photosynthesis

Why can a plant make its own food but an animal cannot?

What is needed for photosynthesis to happen?

How do plants make food and store food?

Why do plants need so much water?

Can plants live in the dark?

Why are plants mostly green?

Teachers are encouraged to make a large circle on the wall using large arrows that can be cut from blue or even black plastic bags. Then cut out white letters to say "Photosynthesis" in the centre of the circle and stick large posters on the arrows to say:

Plants absorb carbon dioxide

Plants release oxygen

Animals breathe in oxygen

Animals breathe out carbon dioxide

Perhaps cut out pictures of plants or get learners to make plants and animals in Art and stick them next to the specific labels they illustrate. Create a glossary by placing words relating to the topic around the classroom. Tell the learners that they are going to be plant investigators, and that their job is to find out what the words mean, and how they relate to plants and photosynthesis.

When introducing this topic remind them of the work on interdependence they covered in Gr. 5. Discuss how animals and plants are interdependent upon each other - plants produce food and oxygen for animals, while animals - when they die - decay, replacing nutrients in the soil for plants, and releasing carbon into the air to continue the carbon cycle.

Plants and food

Green plants are just like factories! They make food for themselves and every animal on earth using sunlight energy, water and the gas carbon dioxide. They also recycle the air and make oxygen for us to breathe.

Scientists have found out exactly how plants are able to do all all these things. Let's take a closer look at how scientists did this and see how plants make food for themselves and us.

photosynthesis

chlorophyll

carbon dioxide

oxygen

glucose

molecule

conditions

anchorage

microbes

fertile

What happens in a factory? Why do you think we can say plants are like factories?

A factory is a place where goods or products are made/assembled/manufactured and then delivered to other places to be used. Plants are therefore like factories as they use raw products to make new products (food).

Why can we say that plants make food for themselves and every animal on earth?

Plants make food for themselves and plants are the beginning of the food chain, therefore all other animals, whether herbivores which eat plants directly, or carnivores which eat the herbivores, depend on plants for food.

The process of photosynthesis

The word photosynthesis is actually has two parts: photo= light and synthesis = to make or put together. So it means to use light to make something (in this case, food).

Photosynthesis is the process that plants use to change the energy from sunlight into energy for food. Plants change light energy from the sun into food energy. Photosynthesis happens in all green parts of a plant. Leaves are usually the greenest parts. So plants do this mostly in their leaves.

Do you remember learning about photosynthesis in Gr. 5? Plants need certain things to photosynthesise.

There are some important requirements for photosynthesis to happen:

1. Chlorophyll: Chlorophyll is a green substance that plants use to capture light energy from the sun. Chlorophyll is very important. Without chlorophyll plants cannot use the sunlight energy to make food. Also, oxygen levels in the air will go down. If that happens plants and animals will suffocate.

As a fun activity, take learners outside to see if there are other colours found in leaves, and not just the green pigment chlorophyll. Although green chlorophyll is predominant, there are also yellow, orange and purple pigments found in leaves, especially in autumn when the leaves change colour. In the body, the pigment melanin, is the main determinant of skin colour and it is also found in hair and the iris in the eye.

2. Sunlight: Sunlight has energy. Plants use this energy to make sugars from water and carbon dioxide.

Scientists have a term for substances like chlorophyll that have a colour. They call them pigments. There are other pigments in plants. Can you think of their colours? There are pigments in your body too! Where do you find them? What do they do?

3. Water: The roots of a plant absorb water and nutrients from the soil. Water is a solvent in all living things. Dissolved substances are moved around the body to where they are needed. Just like you, plants have veins for this movement. They move minerals from the roots upwards. They move sugars from the leaves downwards. Photosynthesis can only happen in a water solution. Water is also important because it provides support to the plant to keep it upright. Like you, plants have skeletons. But unlike you many plants have water skeletons!

In the second term in Matter and Materials, learners will do more on mixtures, solutions and dissolving, and this will therefore make sense. Refer back to this section when you are doing solutions and discussing water as a solvent.

4. Carbon dioxide: The plant absorbs or takes in carbon dioxide from the air through little holes. These holes are found all over the plant, mostly under the leaves.

These holes also allow other gasses and water to enter or leave the plant. They do the same job as your mouth and nose when you breath! The same job as the pores in your skin when you sweat!

5. Soil: The soil provides mineral nutrients and water for the plant that are necessary during photosynthesis. Soil also provides anchorage to the plant, otherwise the plant cannot stand up straight.

The photosynthesis song. http://www.youtube.com/watch?v=C1_uez5WX1o&feature=youtu.be

A really good website on photosynthesis http://www.realtrees4kids.org/sixeight/letseat.htm

How does photosynthesis occur?

Photosynthesis video http://www.youtube.com/watch?v=mpPwmvtDjWw

Plants use chlorophyll, sunlight, water and carbon dioxide to make food. Here is a simple illustration to show how this process occurs:

A diagram illustrating the process of photosynthesis

Chlorophyll captures the sunlight energy.

This energy splits the water into hydrogen and oxygen.

The oxygen is released into the air.

The hydrogen is used with the carbon dioxide to make glucose (sugars).

The sugars are moved from the leaves to other parts of the plants where they are stored.

The water in the plant veins carries the sugars. When the sugars reach the storage parts they are changed into starch.

Plants can store the starch in these places:

leaves (cabbage, spinach, lettuce)

fruit (apples, banana, peaches)

stem (sugar cane)

seeds (wheat or mealies)

flowers (nasturtiums, broccoli and cauliflower)

roots (carrots or beetroot)

Starch is insoluble in water which is why plants store starch and not glucose, which is soluble in water. Refer back to this section when doing soluble and insoluble substances in the second term.

A game on growing plants http://puzzling.caret.cam.ac.uk/pregame.php?game=16&phpsessid=65f1b591e2a1548e0f52d556373966ce

Dramatise the process of photosynthesis

Prepare beforehand by collecting the different materials needed. The characters need different colours to identify themselves as what they are, possibly some t-shirts that they can pull over their clothes, or else a scarf or ribbon or coloured piece of paper to pin onto their front. You will also need tin foil, glitter and string for the roots. For the animals, you can make masks out of paper plates with the eyes cut out, and tied around the head with a piece of string. Learners can draw animal faces on the front.

INSTRUCTIONS:

Your teacher will explain to you how to act out the process of photosynthesis.

Characters needed for this dramatisation:

Narrator to describe the process. This can be a teacher or a learner. It might be a good idea to make short notes from the information above to remember in what order everything is happening.

Sun - this learner can dress in yellow and perhaps get some old tin foil or shiny paper to decorate their head or body to show the light and heat energy that the sun produces.

Plants - a few learners can dress in green and perhaps tie a few strings to their feet to represent roots. They need to hold some rice or shiny glitter in their hands or their pockets to show that the water evaporates after photosynthesis.

Rain / water - a few learners can dress in blue and perhaps have some rice, shiny glitter, small pieces of tin foil or something similar to represent the rain falling.

Carbon dioxide - attach signs to the learner's chests that say 'Carbon dioxide' and dress in purple.

Oxygen - attach signs to the learner's chests that say 'Oxygen' and dress in orange.

Glucose energy as fruit and vegetables - dress up or make posters from scrap cardboard to show large carrots, apples, potatoes, or something similar.

Some learners need to be animals who breathe out carbon dioxide and eat the plants. You can make masks out of paper plates with eyes cut out.

The dramatisation: When the dramatisation starts, the glucose and oxygen actors sit quietly in small groups around the plants with their heads down, not looking at the audience.

The narrator introduces the play and explains the different processes as these occur.

The sun shines in the centre of the stage and can turn and/or raise their arms to show the sunlight radiating from it.

The plants stand away from the sun and the rainwater actors can 'water' them by gently throwing the rice or similar little objects over their heads. Then sit down around the plants.

The carbon dioxide actors run from the animals and circle the plants, and then sit down around the plants.

Now the oxygen and glucose actors rise and run around the plants, and then run to the animals to show they are receiving oxygen and food.

You might want to repeat this a few times to show that this cycle continues.

QUESTIONS:

Why do plants die when there is a drought?

There are many processes which shut down without water, photosynthesis being one of them. Plants cannot photosynthesise sunlight without water. If they cannot photosynthesise they cannot create glucose to support life processes within the plant. If the plant cannot support its own life processes it dies. The plant also loses its support from the water in the veins acting as a 'skeleton'.

Design a poster for your Gr. 4 friends to explain the process of photosynthesis to them. You can use sentences and short paragraphs but make sure you use many illustrations.

Soil was looked at in Gr. 5 Earth and Beyond, especially the particles of soil and which types of soil plants grow best in. However, it would be useful to also emphasise soil in this section and have a discussion on what makes up soil, namely organic and inorganic material, water, air, rocks and sand. Where possible, bring examples of different soil types to class (such as loam soil, clay, beach sand) and get the learners to touch and feel the soil and explore what makes up soil.

Food from photosynthesis

iodine

solution

indicator

starch

test

Photosynthesis is the process inside plants that changes the energy from the sun's light into a form of energy that animals can eat and use to carry out their life processes.

Plants changes the glucose into starch, for example mealies (mealies and maize flour), rice (rice flour and rice) and wheat (flour).

Plants then store this food in different parts of the plant that an animal will eat. They can store it in their leaves, stems or roots, flowers, fruits or seeds.

Look at the images below of different plant products. For each image, identify which part of that plant we eat (for example: When we eat an apple, are we eating the leaf, the stem, the root, the fruit or the seed of the plant?) Use the space below to draw a table for your answers.

Plant

Part that we eat

cabbage

flower

tomatoes

fruit

potatoes

root

broccoli

flower

celery

stem

carrots

root

sunflower seeds

seed

lettuce

leaf

sugar cane

stem

hazelnuts

seed

mealies

seed

bananas

fruit

Cabbage http://www.flickr.com/photos/kewl/6471030841/

Tomatoes

Potatoes

Broccoli http://www.flickr.com/photos/aligraney/661789978/

Celery

Carrots

Sunflower seeds

Lettuce

Sugar cane

Hazelnuts

Mealies

Bananas

We know that plants make glucose (a sugar) but they store starch. Let's now find out what the difference is.

Difference between a starch and a sugar

Prepare beforehand: Prepare at least 10 different plant products in advance of this lesson and mark each item from 1 - 10. Cut up fruit/potato/sweets into bite-sized cubes. Place flour/cooked rice/etc. into bowls. Use teaspoons to taste the flour/cooked rice/etc.

IMPORTANT: Before doing this activity find out if any of the learners have any allergies to these foods and if learners with diabetes are allowed to eat/taste the fruit/sweets.

MATERIALS:

mealie flour

flour

cooked rice, potato, bread

glucose sweets

sugar

sugar cane, if possible

fresh fruit

blindfold

clipboard

INSTRUCTIONS:

Work in pairs.

One partner must be blindfolded.

On a piece of paper list the numbers 1 - 10.

The other partner must let the blindfolded partner taste each of the foods marked 1 - 10. If it is a flour, use a teaspoon to spoon the flour into your partner's mouth. If it is a kernel like a rice or mealie kernel, or a cube of fruit, put it in the palm of their hand and let them eat it themselves.

After each taste your blindfolded partner must guess if it is a sugar or a starch based on the taste.

Record your partners answers on the piece of paper containing the numbers 1 - 10.

Swap with your partner and repeat the test.

While learners are swapping with their blindfolded partners, rearrange the foods with the numbers to ensure fairness. The aim of the test is not to establish the exact name of the fruits and foods but to establish that taste is not a suitable method to test for sugar or starch. Generally sugars are sweet and starches are not, but not always.

QUESTIONS:

Was it easy to distinguish between the sugar and the starch each time? Which foods did you find difficult to classify?

What can you say about the difference between a starch and a sugar based on taste?

Sugars are sweet, starches are not.

Using TASTE to check if a food is a sugar or a starch is not very reliable.

There is a special test that scientists use to see if a food product is a starch or not. It is called the iodine starch test.

Iodine solution is a special solution that is normally a brown liquid.

Iodine is what we call an indicator.

When iodine solution is dropped on starch, the iodine and starch combine and produce a blue colour. We use this to test whether there is starch in a food product.

Let's see how this works!

The iodine starch test

Note: There will be NO tasting in this activity.

MATERIALS:

iodine

the same foods used in the taste test (they should be marked 1 - 10 )

include some other foods such as cheese and a boiled egg

INSTRUCTIONS:

Write the food or plant product that you chose in the first column below.

You are going to test whether this food product is a starch or not. When the iodine solution turns blue-black you will know it is a starch.

Explanation for starch turning blue-black when iodine is placed on it: Starch is composed of polymers of glucose. Long linear chains are amylose. Amylose coils into a structure resembling a tube with a hollow core. Certain molecules, including iodine, can lodge inside the core. The complex of iodine stuck inside the amylose coil produces a characteristic blue-black colour. The starch itself is not altered. NB: This explanation is not necessary for learners, but do say that the iodine reacts with the starch to form a blue-black colour.

Use a dropper and drop iodine solution onto each food group.

Put a tick next to the food product that turns blue-black - this is a starch. Put a cross next to the food product that stays brown - this is not a starch.

Name of Food Product

Starch or not?

1

2

3

4

5

6

7

8

9

10

11

12

QUESTI ONS:

Which test do you think is more accurate to test for starch - the taste test or the iodine starch test?

Did the animal products, such as cheese and boiled egg, contain starch? Why do you think so?

Animals do not produce or store starch. Starch is only stored in plant products.

Animals do store carbohydrates, but not in the form of starch. Only plants produce and store starch. Animals store glucose in the form of glycogen.

Plants and air

All animals and plants need oxygen to live and carry out their life processes.

Animals breathe in oxygen and breathe out carbon dioxide, all through the day and the night. Oxygen is used to release energy from food inside the body, which is used for the life processes.

cell

waste product

cycle

Do you remember what the seven life processes of living things are? Write them down below.

Movement, reproducing, sensing, feeding, excreting, breathing, growing.

Just like animals, plants also use oxygen throughout the day and the night. Oxygen is necessary for plant growth and the development of new plants, seeds, leaves and shoots for example. Plants, therefore, also produce carbon dioxide as a 'waste product' once the oxygen has been used.

Plants do not photosynthesise through the night because there is no sunlight energy available to do that. This means that plants only need carbon dioxide during the day, for photosynthesis.

This cycle of using and producing both oxygen and carbon dioxide is very important to life on Earth.

The oxygen and carbon dioxide cycle

INSTRUCTIONS:

Carefully study the following illustration.

Answer the questions that follow.

The oxygen and carbon cycle

QUESTIONS:

Make a list of living organisms that produce both oxygen and carbon dioxide in this picture.

Tree, reeds, water plants, and shrubs on the bank

Identify three living organisms that cannot produce oxygen in this picture.

Fish, duiker (buck), squirrel, dragonfly

Predict what you think would happen if all the animals were removed from this habitat.

Probably not much would change as the leaves that decay would still give off carbon dioxide for the plants to use, as well as the carbon dioxide that the plants produce themselves.

What two life processes are involved in the carbon dioxide/oxygen cycle?

breathing in oxygen and giving off carbon dioxide

Complete this cycle by filling in the missing information for the two arrows on the left hand side of the illustration. Supply the labels for arrows 1 and 2.

Arrow 1: Plants produce oxygen

Arrow 2: Animals breathe out carbon dioxide

Explain why animals would not survive if all the plants on earth were to suddenly die.

Animals need oxygen for their cells to work and to carry out life processes.

If animals do not have oxygen they cannot carry out the life processes and will die.

Plants also produce food from the sun that animals need to eat for energy to carry out the life processes.

Why do we say the oxygen and carbon dioxide are in a cycle?

For life on Earth to continue, there needs to be an unlimited supply of carbon dioxide and oxygen. It is in a cycle to ensure that similar amounts of both are produced.

Plants produce their own food (glucose) by a process called photosynthesis.

Photosynthesis takes place mainly in the leaves.

During photosynthesis the plant uses chlorophyll, sunlight energy, carbon dioxide (from the atmosphere) and water to make glucose.

Plants change some of the glucose (sugar) into starch which they store in their leaves, stems and roots, flowers, fruits and seeds.

Animals take in oxygen from the air and produce carbon dioxide when they breathe.

Plants recycle carbon dioxide and make oxygen during the process of photosynthesis.

List the four things that are vitally important for plants and photosynthesis.

Sunlight energy, water, carbon dioxide, chlorophyll

Choose words from the word box to complete the following sentences. Write the sentences out in full.

Word box:

organic and inorganic material

photosynthesis

water

air

roots

sand and rocks

The process when the green parts of plants make food is named _____.

Water and minerals are absorbed by the _____ of plants.

Soil is made up of _____, _____, _____, _____.

The process when the green parts of plants make food is named photosynthesis.

Water and minerals are absorbed by the roots of plants.

Soil is made up of organic and inorganic material, water, air,sand and rocks.

The seedlings that were planted in the newspaper cuttings or cotton wool did not grow very well at all, even though they had sunlight and water. What could they not get from the newspaper or cotton wool that plants normally get from soil?

Nutrients and minerals

Where does photosynthesis usually take place? Explain your answer.

Photosynthesis usually takes place in the leaves. The leaves are green as they contain chlorophyll. Leaves also face the sunlight and are exposed to the most sun to drive the process of photosynthesis.

Do you think photosynthesis takes place at night? Explain your answer.

No, it will not take place. At night there is no sunlight energy to drive the process of photosynthesis.

What is the name given to the sugar that plants produce during photosynthesis?

Glucose

What do plants store glucose as? List some places where it is stored.

Starch, stored in leaves, stems, roots, flowers, seeds, fruits.

Nutrients in food

Why do I have to eat so many different things - why can't I just eat what I like?

I have heard that people say: 'You are what you eat...' - what does that mean?

What is so bad about sugary sweets - why shouldn't I eat lots of them?

What is the difference between a fat and an oil?

Food groups

Learners must collect the wrappers and packaging material of the food they eat for the activity that follows. Advise them to wash all tins or plastic that still contains food particles to avoid nasty odours and insect infestations in your class!

All living plants and animals need to feed or eat to give them energy to carry out the life processes. Plants make their own food from sunlight, water and carbon dioxide through the process of photosynthesis. Animals cannot make their own food and need to eat plants or other animals to get energy. People also have to eat plant or animal products to get energy to grow and develop.

Classification of food groups

The food we eat can be grouped or classified into different types or groups. We call these food groups. There are a four main food groups and each food group does a different job in the body:

classification

carbohydrates

proteins

vitamins

nutrition

pyramid

immune system

insulate

carbohydrates

proteins

fats and oils

vitamins and minerals

Examples of the foods in the food groups; carbohydrates, proteins and fats and oils.

We classify food according to these food groups, although most foods contain a mixture of more than one nutrient group.

Let's look at each food group separately and see why each one is important:

Carbohydrates:

They are the most important source of energy for the body.

They store energy for the body.

Carbohydrates are an important part of the body structure.

Foods that contain carbohydrates are: pasta, samp, potatoes, cereal, mealie meal, porridge and bread.

Bread

Rice

Pasta

Potatoes

Proteins:

Proteins are the building blocks for our body - they build the body's muscles.

They also help to repair hurt or broken tissue.

Proteins can be used as reserve energy if there is a shortage of carbohydrates.

Some foods that contain proteins are: meat, fish, chicken, eggs, beans, milk and cheese.

Protein is also found in many plant products: chickpeas, beans, lentils, nuts and soya.

Meat

Lentils

Almond nuts

Cheese

Lipids - fats and oils:

Fat is stored around organs like the kidneys to protect them from injury.

Fat is also stored under the skin to insulate us (keep us warm).

Fat can be used as reserve energy if there is a shortage of carbohydrates.

Foods that contain fats include: butter, margarine, sardines, cooking oils, nuts, peanut butter and avocado pears.

Mixed nuts

Cooking oil

Peanut butter

Margarine

Vitamins and minerals:

Vitamins and minerals are essential to the human body and yet we produce very few of them ourselves.

Many important minerals are contained in the food we eat. Two of the most important are:

Sodium that helps to keep the correct balance of water in the body and is found in most food.

Calcium that is important for strengthening of bones and teeth. Calcium can be found in fish, green vegetables, milk and cheese.

Most vitamins are manufactured by plants, so we get vitamins from the food we eat or from vitamin supplements.

There are specific foods that contain specific vitamins. The table below shows some important vitamins, their natural sources and/or the food that contains them and some of their functions in the human body.

Name of vitamin

Sources

Function

Vitamin A

Egg yolk, liver, deep-yellow and deep-green fruits and vegetables, fish liver oils

Enables the eye to produce a pigment that helps us to see in dim light.

Vitamin B

Brown rice, whole-wheat bread

There are several types of vitamin B and they have many functions, e.g. they are important in the chemical reactions of breathing.

Vitamin C

Citrus fruit, strawberries, tomatoes, peppers

Strengthens the body's immune system by increasing its ability to fight infections.

Vitamin D

Egg yolk, fish liver oils, can be made in the skin when the ultra-violet rays from the sun convert cholesterol in the skin to vitamin D

Helps the absorption of calcium and phosphate. These nutrients are used for the making of strong bones and teeth.

Milk is a source of calcium.

Fruit and vegetables are sources of vitamins.

A simulation about eating and exercise

Classifying food into the different food groups

MATERIALS:

Collect wrappers and packaging material, like boxes and tins, of the foods you eat and bring these to school.

INSTRUCTIONS:

Work in groups of 2 or 3.

Choose the 3 foods that you think are the most healthy to eat from the different wrappers and boxes that you have in your group. Write a reason next to each of these 3 choices why you think they are really healthy.

Locate the LIST OF INGREDIENTS on each food container. You should have at least 10 different containers. (If you have too few, swap with another group when they are finished with theirs.)

Sort the different foods into the major food groups.

Record your work in the table below.

Carbohydrates

Proteins

Lipids

Vitamins and Minerals

Very often food manufacturers add different preservatives, flavourings and colourings, as well as salt and sugar, to make the food look or taste more attractive to their customers. These are called additives.

Read the ingredients on your 10 packaging labels again.

In the first column, write the name of your product.

Tick (✓) under each column if your product has any of these items added to it.

The first one is done as an example.

Food

Additives

Salt

Sugar

Others

EXAMPLE

Bread

✓

✓

✓

1

2

3

4

5

6

7

8

9

10

Make a list of the main flavourings that were used in your products.

What preservatives are used most often by the food manufacturers?

Look at the 3 foods you said were the most healthy at the beginning of this activity and why you said they were healthy options.

Read their packaging details - which additives do they contain?

Do you think these additives make these products healthier or less healthy to eat?

After reading the labels do you still think these are the 3 most healthy foods? Explain your answer.

Compare the other labels and decide if there are perhaps other healthier foods on your list.

After doing this activity, did you notice a difference between foods which are naturally occurring (such as meat and vegetables) and foods which have been processed?

The natural foods contained a mixture of more than one nutrient group. For example, nuts are a source of protein and fat. Milk is a source of calcium and protein. Vegetables contain many nutrient groups.

The foods which have been processed, or manufactured, often contained additives, such as salt, sugar, preservatives and flavourings.

SUGGESTED PROJECT - If required, teachers can use this opportunity for a small research project on additives and the pros and cons of eating foods with additives.

Let's have a look at some different meals to see if we have all the food groups.

Sorting foods in a meal into the food groups

INSTRUCTIONS:

Below are pictures of five different meals.

Study each meal and classify each food on the plate into one of the food groups (protein, carbohydrates, fats and oils, vitamins and minerals).

Remember, some foods may contain more than one food group.

In the table, write out each food in the meal, and next to it, write the food group it belongs to.

Meal

Food groups

QUESTION:

Which meal do you think is the healthiest? Explain your answer.

In the next chapter we will look more at what makes up a balanced meal.

Food groups:

foods for energy - carbohydrates

foods for growth and repair - proteins

foods for storing energy (in the form of body fats) and providing insulation and protection for nerves and organs - fats and oils

foods for maintaining a healthy body and immune system - vitamins and minerals

Most natural foods contain a mixture of more than one foor group.

Most processed (manufactured) foods have added salt, sugar, preservatives, flavourings and colourings.

Write the sentence out in full below and fill in the missing words.

Foods are classified into the following food types, carbohydrates, _____, proteins and _____.

Name 3 reasons why lipids are important in our diet.

Fat is stored around organs for protection. Fat is stored under the skin to insulate us. Fat can be used as reserve energy if there is a shortage of carbohydrates.

List 3 sources of proteins.

Meat, fish, chicken, eggs, beans, milk, cheese (accept any 3 sources of protein).

Why is it necessary to supplement our diets with vitamins?

Allow learners to give their own reasons.

Complete the table below which shows some important vitamins, their natural sources and functions.

Name of vitamin

Sources

Function

Vitamin A

Enables the eye to produce a pigment that helps us to see in dim light

Brown Rice, whole-wheat bread

There are several types of this vitamin and they have many functions in the chemical reactions of cellular respiration

Vitamin C

Strengthens the body's immune system by increasing its ability to fight infections

Vitamin D

Egg yolks, fish liver oils, can be made in the skin when the ultra-violet rays from the sun convert cholesterol in the skin to vitamin D

Name of vitamin

Sources

Function

Vitamin A

Egg yolk, liver, deep-yellow and deep-green fruits and vegetables, fish liver oils

Enables the eye to produce a pigment that helps us to see in dim light

Vitamin B

Brown Rice, whole-wheat bread

There are several types of this vitamin and they have many functions in the chemical reactions of cellular respiration

Vitamin C

Citrus fruit, strawberries, tomatoes, peppers

Strengthens the body's immune system by increasing its ability to fight infections

Vitamin D

Egg yolks, fish liver oils, can be made in the skin when the ultra-violet rays from the sun convert cholesterol in the skin to vitamin D

Used for the making of strong bones and teeth

What are some of the additives that processed foods contain?

Salt, sugar, preservatives, flavourings, colourings

A vegetarian is someone who does not eat meat. What other foods, besides meat, should they be eating and why?

A vegetarian might not get enough protein. They should eat other sources of proteins such as eggs, beans, cheese and other dairy products and nuts.

Nutrition

I love eating fast foods but why does my mom say it is not good for me?

Why must I eat my vegetables if I just want to eat protein, bread and pasta?

Can I get sick if I do not eat the right foods or not enough of a certain type of food?

A balanced diet

Now we know that there are different foods that are classified into the four food groups. The next step is to see what amounts of each food group we need to eat regularly to stay healthy. This is called a balanced diet. What is a diet?

diet

balanced

Discuss the word 'diet' with your class and come up with a definition for this word. Write it below.

For nutritional scientists (people who study the effects of diet on health and well-being), the word 'diet' means the sort of food that people regularly eat. When we say we eat a healthy balanced diet we mean that we eat food that contains adequate or the right amounts of all the nutrients our body needs to function.

Food pyramids

A food pyramid provides a guide to a healthy balanced diet. It shows how to classify food types into different levels. A balanced healthy diet will include servings from each level of the food pyramid and will show the correct quantities you need to eat:

You need to eat a little of the food at the top (oils, sweets, etc.)

The food in the middle of the pyramid, fruit and vegetables, must also be eaten in fair amounts.

You should eat less meat, chicken, fish and other proteins than vegetables and fruit.

You need to eat more of the food at the bottom of the pyramid (breads, pastas, rices, etc.).

Here is an example of a food pyramid:

A food pyramid

Some people eat a very unhealthy diet and turn the food pyramid upside down! They eat far more sweets, cakes, fatty rich food and far less vegetables and starches!

Evaluating a diet to see if it contains all the food groups.

MATERIALS:

a record of the weekly diet of Rajesh

INSTRUCTIONS:

Carefully study Rajesh's weekly diet.

Answer the questions that follow.

Breakfast

Lunch

Supper

Monday

toast with peanut butter, coffee with milk and 3 teaspoons of sugar

two-minute noodles, cream soda, jelly (while watching TV)

spaghetti bolognese (with chopped carrots in the mince) with cheese sprinkled on top, fruit juice, tea with milk and 2 teaspoons of sugar

Tuesday

toast with peanut butter, coffee with milk and 3 teaspoons of sugar

two-minute noodles, Coke, toast with peanut butter, popcorn (while watching TV)

Mom and Dad worked late - scrambled egg on toast with baked beans; coffee with milk and 3 teaspoons of sugar

Wednesday

late for school - didn't eat.

2 eggs and toast with cheese, tea with milk and 3 sugars, more toast with jam and peanut butter later (while watching TV)

Hawaiian pizza, coke, cream soda, chocolate milkshake

Thursday

toast with peanut butter, coffee with milk and 3 teaspoons of sugars

indoor hockey practice after school - pie from tuckshop and Coke, chocolate and packet of hot chips

roast chicken, butternut, baked potatoes, salad, fruit juice, coffee with milk and 1 teaspoon of sugar

Friday

toast with butter (peanut butter is finished), coffee with milk and 3 teaspoons of sugar

band practice after school - pie and coke from tuckshop, sweets

takeaway chicken in a bucket, hot chips, Coke, tea with milk and 3 teaspoons of sugar, popcorn

QUESTIONS:

Reading only this table showing Rajesh's weekly diet, do you think he has a balanced diet? Why do you think so?

Assess the learner's capability to make conclusions from the data presented. Rajesh does not have a balanced diet for a few reasons. He consumes a lot of sugar, oil and fat in the sweets, Coke, takeaways and sugar in his drinks. He also has a lot of starch, but not much fresh fruit and vegetables.

Now let's use our knowledge of a food pyramid to see how healthy Rajesh's diet for the week was. Use the tallying method to keep score of everything he ate: to tally up results you make one line down for every item you count and when you get to the fifth item you draw a diagonal line through the other four. That makes it easy to count in fives and count the few left over at the end.

Total Fats and Oils

Total Proteins

Total Vitamins and Minerals

Total Carbohydrates

List the times and days when Rajesh ate fruit or vegetables.

On Monday, Rajesh had carrots in the spaghetti bolognaise and on Thursday he had salad and butternut with his meal.

What important food group is Rajesh missing from his diet if he does not eat enough fruit and vegetables?

He will not be getting enough vitamins and minerals.

Can you predict what will happen if Rajesh continues with this diet?

If he is not already very overweight he soon will be overweight and may develop problems that accompany this - diabetes, bad skin, aching joints, greater risk of heart disease etc.

Now that you have tallied up the different food groups that Rajesh ate in a week, do you think he ate a balanced diet? Why do you say so?

Rajesh's diet was not balanced because Rajesh did not eat the correct quantities of food from the different food groups and therefore I don't think their diet is very balanced.

Do you think Rajesh is a very active person? Why do you say so?

He lies in front of the TV most afternoons, and his only extramural activity is band practice, which is not very energetic. Indoor hockey once a week is probably not enough exercise.

Takeaways are known for being fatty and oily because restaurants often prepare the food in deep oil. Rajesh's family ate takeaways twice in the week and the mom cooked twice. Compare the cooked meals with the takeaways specifically focusing on the amount of oil used to prepare the meals.

The bolognese and the roast chicken were probably prepared at home and the pizza and 'bucket' chicken were probably takeaways. The roast chicken meal included a lot of vegetables and the bolognese included carrots in the mince as is the tradition in many homes. These meals are far healthier than the oily chicken or pizza that they had because they contain fewer oils and more vegetables.

What advice would you give Rajesh?

Learners should include something about eating a more balanced diet, which would include eating more fresh fruit and vegetables and less fats, sugars and oils. Rajesh should cut down on the amount of sugar he puts in his hot drinks, he should always eat breakfast in the morning, he should not rush when he eats his meals and just buy food from a tuck shop. Rajesh should also become more active and not just lie in front of the TV for the afternoon. Rajesh should also consider talking to their parents about the meals they are given in the evening. They should not have takeaways so often and the parents should also take responsibility for what their children eat.

Now that you have completed this activity, explain why different portions of the different food groups are necessary for a balanced diet?

Comparing meals

INSTRUCTIONS:

Below are photographs of different meals for breakfast, lunch and dinner.

One of the meals is unhealthy and the other meal is healthy.

Choose which is the healthier option and write a paragraph explaining why. List the food groups that are missing from the unhealthy option compared to the food groups that are present in the healthy option.

Breakfast:

Option 1: Fruit loops

Option 2: Fruit salad

The fruit salad is healthier as it contains a variety of fresh fruit which will satisfy some of your daily requirement of fruit and vegetables. The fruit loops are unhealthy as they contain a lot of sugars, colourants and flavourants. They do not have any nutritional value.

Option 1: Oats with raspberries

Option 2: Flapjacks with syrup

The oats with raspberries is more healthy compared to the flapjacks with syrup. Oats is a good source of nutrition and the raspberries are very high in vitamins. The flapjacks are unhealthy for breakfast as they contain a lot of fats and sugar.

Lunch:

Option 1: Egg salad

Option 2: Fried chips

The egg salad is the healthy option. This meal contains a variety of food groups as there are fruits and vegetables containing vitamins and minerals and the eggs are a good source of protein. The fried chips are very unhealthy as a meal as this only consists of one food group (starch) and there is added oil from the frying.

Option 1: Hamburger

Option 2: Omelette with salad

The omelette is the healthy option. As with the egg salad, this meal contains fresh salad and the eggs are a source of protein. the omelette possibly has meat or mushrooms and cheese which also adds to the nutritional content. Although the hamburger contains meat, starch and cheese, it was probably prepared in an unhealthy way. Consider that the meat was fried in oil and that the bread has less nutritional value than vegetable starches. This meal also lacks fresh fruit or vegetables.

Supper:

Option 1: Chicken pieces

Option 2: Beef, peas and rice

The beef, peas and rice is the healthy option for supper as the meal contains starch (rice), meat for protein (beef) as well as vegetables (peas). The other meal is unhealthy as it only contains one food group, namely protein from the chicken pieces.

Diseases caused by an unhealthy diet

There are many people in the world that do not or are not able to eat a healthy, balanced diet. Many choose to eat an unhealthy diet while others do not have a choice.

Many people live in cities and can afford to buy takeaways often, or to eat hastily prepared meals that do not always include foods from the 4 food groups.

nourishment

overeat

obesity

diabetes

Remember the food pyramid we saw before? Below is a picture of the food pyramid of someone with an unhealthy diet.

The food pyramid of an unhealthy person's diet.

Discuss in your class why you think this kind of food pyramid is unhealthy. Compare it to the healthy food pyramid and write down some of the differences below.

This food pyramid is out of proportion compared to the previous one and does not form the shape of a pyramid anymore. This is because the person eats a lot more fats and oils compared to how much they should eat in a healthy diet. The amounts of meat and dairy products are about the same. But, there is a lack of fruit and vegetables in the diet. This is very unhealthy as the person will not be getting enough vitamins and minerals in their diet.

Some families have to eat what they can afford. They do not have the privilege of choosing what their food pyramid looks like but eat what they can buy with their small incomes. This would mostly consist of carbohydrates and some vegetables, and rarely includes meat and enough proteins and other vitamins.

Let's look at the causes of a poor, unhealthy diet and then at possible diseases that may arise from this.

Causes of a poor diet

There are many causes of a poor diet.

Diseases and infections: When someone has a chronic illness, such as HIV/AIDS, they are sick for a very long time. Their bodies become weak and they cannot take in nourishment from the food they manage to eat, resulting in a poor diet.

Dietary practices: In many countries, people have a preference for certain foods, for example rice, samp or mealie meal. People eat a lot of this particular food type and do not get enough protein or fats and oils in their diet. They also often cannot afford other food types, especially in developing countries. However, some families in developed countries do not eat enough fruit and vegetables out of choice and eat a lot of refined carbohydrates which also leads to disease and illness.

Poverty and high food prices: Poverty and high food prices stop many people from enjoying foods such as milk, meat, poultry (like chicken) and fruits. This has made it almost impossible for poor families to afford certain food groups. Some families can only afford one type of food group.

Food shortage: Sometimes famine occurs in a country where drought, poor farming knowledge and skill, and a lack of technology limits the yield of crops and herds of animals. This results in a food shortage in that country.

In these situations, people will eat whatever food is available to them, often leading to an unhealthy diet.

A balanced diet also means drinking water throughout the day!

An unhealthy diet can lead to many health problems because the body does not get the right amount of the different food groups and therefore cannot function properly.

Some diseases and conditions

It is not necessary for learners to know the difference between a disease and a condition, but generally a "disease" refers to an illness or some deviation from the normal functioning of the body or organ. A "condition", however, is a more broader term and often refers to the state of something.

Often we get diseases and conditions because our bodies do not get the necessary nourishment. Some of these diseases are:

Tooth decay: When you eat or drink too much sugar, the bacteria in your mouth makes acids that eat away at the tooth surface (called enamel), and causes cavities to form.

Too many sweets can cause cavities to form in your teeth.

Remember to brush your teeth to help prevent tooth decay! http://www.flickr.com/photos/seeseecards/7209691478/in/set-72157629756301182/

Rickets: This is a condition mostly seen in babies and children. When children do not get enough fruit and vegetables and do not get enough Vitamin D, their bodies cannot absorb calcium and they cannot grow strong bones.

Constipation: This is a painful condition (not a disease) that occurs when bowel movements become difficult and take place days or even weeks apart. An unhealthy diet is often to blame, but there are other causes too. The best way to treat constipation is to eat a healthy diet with lots of fibre in the carbohydrates, to exercise regularly and to drink plenty of water.

Obesity: This is a condition (not a disease) where a person's body weight is more than 20% that of the average weight for other people the same age and height as that person. The best prevention for obesity is to follow a healthy, balanced diet.

e.tv news story on obesity in South Africa http://www.youtube.com/watch?v=DRp0OY9Li1o

Obesity is a condition which is becoming more common all around the world. http://www.flickr.com/photos/78428166@N00/4296824658/

Diabetes: This is a disease that affects the body's ability to use blood sugar for energy. Diabetes symptoms may include an increased thirst and urination, blurred vision and excessive tiredness.

What is diabetes? (video) http://www.youtube.com/watch?v=4EEtubB74lM

Anorexia nervosa: This is life-threatening eating disorder where the patient starves themselves and deprives their bodies of nourishment to cause themselves to lose tremendous amounts of weight.

Kwashiorkor: This is a disease that affects many children. It is a lack of protein and iodine in their diet. Children suffering from this may have swollen hands and feet, and especially a very large tummy, many ulcers on the skin and their hair might discolour.

What diseases or symptoms could Rajesh, develop from his diet?

INSTRUCTIONS:

Carefully read through Rajesh's diet again.

Evaluate his activities in the afternoon as well.

Use the information about these diseases and disorders and suggest possible diseases or conditions that Rajesh might develop if he does not change his diet drastically.

Disease

What in Rajesh 's diet could cause this disease?

Answers:

Disease

What in Rajesh's diet could cause this disease?

Obesity

Overeating and inactivity

Rickets

Possibly because of the small amount of fruit and vegetables eaten

Diabetes

Eating far too much sugar and starches, inactivity

Constipation

Rajesh is very inactive and almost never drinks any water!

Research one of the diseases

This can be used as a possible project, where learners can also present their posters to the class and practise their oral skills. Be sensitive to the fact that some children in your class may suffer from some of these diet-related diseases.

MATERIALS:

books from the library, information from the internet

sheets of paper

coloured pens and pencils

INSTRUCTIONS:

Choose one of the diseases that is related to an unhealthy diet and do some extra reading and research around the topic.

You must prepare a poster about this disease or condition.

On your poster, you must include information about the causes of the disease, which people are most likely to suffer from it and why, the symptoms, the health risks, and any possible treatments.

You might have to present your poster to the class, depending on your teacher.

A diet refers to the selection of food we eat every day.

A balanced diet contains sufficient quantities of food from all 4 food groups, as well as water and fibre.

Some diseases can be related to diet.

What do you understand by the term "balanced diet"? Write a description below.

Draw a food pyramid of the food that you eat and assess whether it has the correct shape of a balanced diet.

(Mark individual learner's food pyramids based on the one used earlier in the book.)

Rajesh thinks that he can get enough water in his diet by drinking Coke and coffee with sugar in it. Explain to him if this is true or not and why.

Write a paragraph where you explain some of the possible causes of a poor diet.

Food processing

How do we make food last longer?

Is it possible to stop food from going off?

What can you do to prevent bacteria and germs getting into food?

Introducing this topic

This topic forms part of Food Science which is an exciting branch of Science that incorporates Chemistry, Biology and Physics with real-world applications.

Remind students that this term's work has focused on how food is made through photosynthesis and the important role that plants play in this process. We then moved on to investigate nutrition and the importance of a balanced diet before looking at the diseases and health problems associated with a poor diet. In this chapter we'll look at food processing and how humans have devised ways to keep food healthier for longer.

This is an excellent website for lesson plans and support materials: http://www.jhsph.edu/research/centers-and-institutes/teaching-the-food-system/curriculum/food_processing.html

Why do we need food processing?

People have been processing food for thousands of years. Before the invention of fridges and freezers, people had to collect food in summer and store it because in winter food is often scarce. They found out that they could preserve food like meat and fish by salting and spicing, and then drying it - this is called curing the meat. In South Africa biltong and bokkoms are examples of cured meat and fish.

processing

preserve

cure/curing

artificial sweeteners

preservatives

Bokkoms (cured fish) http://www.flickr.com/photos/salsaboy/2449275663/

Pieces of meat are hung up to dry and turn into biltong. http://www.flickr.com/photos/55530505@N08/5148999033/

Drying foods (video). http://www.youtube.com/watch?v=FKSgyjk_e3c&feature=related

A time-travelling role play

This is a chance for learners to be creative and use their imaginations. Encourage them to do so. If time does not permit, the learners do not have to actually make the objects to take with them. But allow them time to discuss the possible objects they could make in their groups. They can then draw some designs and report back to the class as a group.

Work in groups of 4 - 5

You are time-travellers and you are preparing for your first jump through the wormhole! You may not take anything non-organic with you so no metal tins or plastic containers, and certainly no computers, cell phones or laptops!

Biltong was invented by the Voortrekkers who travelled by ox-wagon during the Great Trek. They needed to preserve meat for the long journey. The raw meat was preserved using salt, vinegar and spices.

Imagine being transported 250 years back into history and arriving with only the clothes you are wearing and whatever you have learnt in your head in EXACTLY the same place you are right now. It is late summer and you need to spend a year wherever you are and survive until the wormhole opens again at that exact spot and allows you to return to 'the future'.

Your mission: gather as much information on the local inhabitants and the food they eat, their ways of living and how they survive the elements and natural dangers in their environment. When you return you will need to explain how they preserved and processed different foods to last them through winter and how they packaged and protected this food from scavenging animals and pesky insects.

Brainstorm this problem with your group. List as many different questions or problems that you can think of that will affect you:

immediately,

in about a month's time,

in 6 month's time, and

right at the end of your stay - a week or so before you return to the present time.

Think especially of food and shelter, and specifically how you will collect, preserve and process any food that you collect. Remember you are not allowed to take anything that is not organic so no pocket knives, nylon rope or even lighters can go with you!

Design the following items that you can make and use when you land.

Something that you can collect and carry water in, and store it for 'the future'.

Something that you can collect and carry food in, and specifically something that you need to store it in to keep it away from scavenging animals and insects.

Something that you can use to cut with - you will need to make a shelter to sleep in and keep safe from wild animals; and also cut material for your food and water containers.

Something that you can use to hunt animals or catch fish if you are going to eat meat while you are there.

A device that you can use to preserve meat or fish, or perhaps fruit and vegetables for the winter months.

Give each person in your group one of these items to make and bring to class. Make sure you do not use any modern tools or any metal, glass or plastic as it is highly unlikely that you would have any such items to use 250 years ago.

QUESTIONS:

List the possible dangers that you will face in your new 'home'.

Can you predict how the locals will look and how they will treat you?

Describe your first night there.

Explain how you will decide what you can and cannot eat on your first day.

Complete this sentence: If I want to preserve some of the fish I catch, I will...

The local indigenous people use different methods to preserve their fresh fruit and vegetables. Find out about these methods and use one method to preserve some fruit of your own. At the end of this chapter, bring your preserved fruit to show the class. You have two weeks.

Introducing this lesson:

Start this lesson by brainstorming different types of processed foods and facilitating discussion to try and agree on a class definition for 'processed food'. It should be clear after this discussion that:

Almost all the food we eat is processed in one way or another.

Food and beverage companies change raw animal and plant products into food that we can eat or drink through various processes. This is called food processing.

Food processing can include: cooking, baking, roasting, grilling, smoking, drying, spray drying, juice concentrating, freezing, milling (wheat), and sometimes slaughtering animals for their meat is also considered a form of food processing.

We process food to make it more edible (preparing / cooking), last longer (preserving) and to increase the nutritional value (fermenting).

Make a class list of possible reasons WHY food is processed and possible examples of people who would benefit from this processing - write this on newsprint or poster paper to refer and add to as you go.

Food Processing - Then and Now

Hundreds of years ago explorers like Columbus, Da Gama and Diaz, had to pack supplies for their crews to last a very long time should they not find food and water on their expeditions. They too had to take as much preserved food and drink as they could.

Many of the foods we eat today cannot be eaten in their raw form - we need to process the food to make it edible.

Sometimes food is also processed to add to its nutritional value, for example when we ferment dairy products to make yogurt, cheese and buttermilk.

There are many reasons to process food. Can you think of any? Write them down below.

When you get home today ask your parents, family members and maybe your friends' parents if they think processed food is good or bad and why they say so. Write the results of what you learnt from this quick survey below.

Benefits of food processing

Food processing adds many benefits to our modern lives:

The Emperor of France, Napoleon Bonaparte, launched a competition in France in 1975 to develop ways to preserve foods for France's armies! This led to the discovery of canning.

Transportation of fresh food is quite difficult. If producers can process the fresh fruit and vegetables in some way, the food is easier to transport. Delicate products like grapes, strawberries and peaches can be transported much more easily when they are preserved than if they were fresh. The processing also helps the fruit and vegetables to last longer.

This truck collects the pear and apple boxes and transports them.

Today people can eat fresh fruit and vegetables all year round and do not depend on seasonal availability because of modern methods to process and transport these products. Therefore, food processing and transportation makes the modern 'balanced' and varied diet possible.

Many times food and beverage producers add extra vitamins and nutrients to their food to make it healthier for their clients.

Buying and preparing processed food is also more convenient and less time-consuming.

Foods are processed to preserve them, for example when fruits are preserved to make jam, or pickled (eg. pickled onions).

Making cheese at home (video) http://www.youtube.com/watch?v=AWx8VlnT8ZY

This ginger has been preserved so that it lasts longer.

Pickling vegetables (video) http://www.youtube.com/watch?v=103mpng1Jp8&feature=related

Food processing is lastly very important to people with allergies and diabetes because they are able to eat a greater variety of healthy food. An allergy for cow or goat milk is a very common allergy among small children. They are able to drink 'milk' only because modern food processing has found a way to make milk from rice, oats or soya.

Making plum jam (video) http://www.youtube.com/watch?v=eFIPGpiS9bM&feature=fvwrel

Rice or soya milk are processed foods and an alternative to cow's milk for people with allergies.

Describing processed foods

INSTRUCTIONS:

Look at the following photographs of various foods.

Each one has either been processed in some way, or needs to be processed before we can eat it.

Briefly describe why and how each food has or will be processed.

Food

Reason for being processed

Raw meat

Yoghurt

Pickled gherkins

Glacé cherries

Fried eggs

Cheese

Butternut

Frozen meals

Possible drawbacks of processed food

We have seen that processed foods have many advantages in our modern lives, but processed foods also have drawbacks (disadvantages), especially if they have been over-processed.

Write down some possible reasons why people think processed food is not good for you.

Class discussion

INSTRUCTIONS:

We are going to have a class discussion about some of the possible drawbacks of processed foods and why some people do not like the idea.

This is an opportunity for you to practise taking down notes from what was said in class.

Your teacher will lead the discussion and also write some things on the board.

You must take notes in the space below.

Class discussion: Discuss the results of their homework surveys with the class and make a mindmap on the board showing the possible reasons why people do or don't think processed food is good for you.

The following information must be used to facilitate the class discussion. Make sure to write the main points on the board so that learners can copy the main headings down. Also encourage learners to take down some additional notes. This is an important skill for their school career.

There are different ways to process food, but in almost all of these ways some of the nutrients, vitamins and minerals are destroyed. Any process that uses heat generally also destroys Vitamin C, for example. However, people tend to think that here is very little nutrients left in processed food when this is actually not the case. Research has shown that only between 5% - 20% of nutrients are lost when food is processed - in a factory or a home. The amount of nutrient loss depends on the method used to process the food.

You might have heard that there are dangerous additives in processed food that make it very bad for you. In the past many food manufacturers have in fact added many extra products to food:

Preservatives: preservatives, such as sulfur dioxide, are added to food to make it last longer. These are not always very healthy.

Colourings: Many food and beverage manufacturers used to add all sorts of artificial colourings to food to make it look more attractive to their consumers - a bit like adding paint to your food! Nowadays, with many consumers complaining, they no longer do this but only add natural colourants that can be made from berries or plants for example.

Artificial sweeteners, salt and flavourings: Manufacturers also used to add artificial sweeteners and flavourings, such as MSG (monosodium glutamate), that are cheaper and allow them to make a larger profit. Artificial flavourings are not very healthy and can cause organ and brain damage. Many people are also allergic to these products. Therefore, many companies have stopped adding artificial sweeteners, salt and flavourings and have instead chosen to add natural products instead.

Governments around the world have drawn up very strict laws that control the additives that get added to food and beverages, and food manufacturers have to be incredibly careful what they add nowadays. Only additives that have been proven to be safe for humans to eat or drink may be added to food.

How are foods processed?

Introducing this topic:

The CAPS require that learners research different ways of processing food (raw material) and then choose one way and process food (raw material) using this method. We have set this out as a project that teachers can use to assess. The unit briefly introduces some of the ways of processing food and very briefly touches on each of these. Learners are then required to research their preferred method and present their research using various methods, like posters / slideshows in PowerPoint / etc - about this method of food processing. They also need to process food (raw material) using this method and demonstrate the steps they followed to their class.

There are different levels of food processing. The key question is to ask: has any process occurred from when this plant or animal was in its natural habitat to where it is now? If you can say yes then you know that it has been processed in some way or another.

shelf-life

Levels of food processing

Minimally processed foods:

Fruit and vegetables, nuts, meat and milk undergo very little processing from when the plant or animal product was in its natural habitat to the point where it lands on your table.

They need to be harvested, washed and sometimes peeled, chopped, juiced or cut to remove inedible parts, before they are sold. These have a very short shelf-life.

Milk and juice are minimally processed.

Many indigenous South African cultures leave milk to curdle in a hide sack or calabash to form a favourite semi-solid, sour yoghurt drink. This drink is called amasi.

Vegetables are washed, cut and cooked. This is minimal processing.

Processed food ingredients:

Products with a longer shelf-life, like flours, oils, fats, sugars, syrups margarine, sweeteners and starches, fall into this category.

The original product has been changed and the ingredient does not look like the original kernel or grain, or oil seed or beans.

These processing techniques often break down any nutrient values and the manufacturers often add in extra nutrients, vitamins and minerals to their foods.

Highly processed foods:

Highly processed foods include snack foods and desserts, biscuits, cereal bars, chips, cakes and pastries as well as soft drinks and breads, pastas, breakfast cereals and infant formula.

Animal products that are highly processed include processed meats (smoked, canned, salted or cured, nuggets, fish fingers, viennas, many sausages and boerewors, and burgers).

Mealie meal made by grinding maize forms a huge part of the diet in many indigenous cultures in southern Africa, such as the Ndebele, Zulu and Swazi.

Polony is a highly processed food.

The table below shows how a raw product is processed to make a raw ingredient which looks very different to the original raw product. Then the processed raw ingredients are used to make highly processed foods, such as bread.

The raw product: Wheat

The processed ingredient: Flour

The highly processed food: Bread

The Swazi people make Marula beer by placing the ripe fruit in large traditional pots and letting them ferment.

Learning how to summarise

Sometimes we are presented with a lot of information and we need to condense it to make it easier to remember. This is called summarising and it is a very useful skill.

INSTRUCTIONS:

Use the space below to draw a table to summarise the information above about the levels of food processing.

Include a short description of the level of food processing and examples.

Think about how many columns and rows you will need.

Give your table a heading.

This question is aimed to help learners to summarise information into a table format. If they are finding this difficult, start them off with drawing the outline of the table on the board and filling in some of the information. One possible solution for a table is given below.

Level

Minimally processed foods

Processed food ingredients

Highly processed foods

Description

Products that undergo very little processing

Products that have been drastically changed and the ingredient does not look like the original

Products consisting of a combination of processed ingredients.

Examples

Fruit and vegetables, milk, nuts, meat

Flour, sugar, oil, syrup.

Snacks, biscuits, desserts, meat products such as fish fingers, boerewors, etc.

Food processing methods

As you could see in the above breakdown, the degree in which food is processed determines many of the food preserving processes involved.

Dr J. H. Kellogg invented a type of granola cereal in 1860 - it was meant for Seventh Day Adventists who were following a very strict diet. Later his brother joined him and they started their company Kelloggs! Do you think they were successful?!

Food processing methods have changed in many ways, but the basic principles are still applied. Food is still dried or heated to preserve it, just like people did 300 years ago, but there are many modern methods that are also used today.

sun drying

fermenting dairy into cheese, buttermilk (Amasi) or yogurt, or barley or grapes

pickling vegetables (onions or gherkins, for example)

salting and spicing meat to preserve it (then drying it)

adding sugar to berries and/or fruit to make preserves

pasteurisation: using just the right amount of heat to warm up milk or juice for example, to extend the shelf life

cooking: roasting, smoking, baking, frying

toasting

freezing or refrigerating

freeze drying

spray drying

making juice concentrates

The Ndebele people of southern Africa eat a plant called Umrorho. It is cooked or dried by spreading it out in the sun so that it can be stored for the cold winter months.

When you go home from school today, make a list of the food products that you have at your house (whether they are in the cupboard, the fridge or the freezer). Next to each item, write down the type of processing it might have gone through, using the list above as a guideline.

No matter what food processing method is used, there are 5 extremely important performance parameters that all food processing must adhere to:

hygiene

energy efficient

minimal wastage

labour efficient

minimal factory shutdowns

Discuss why you think each of these 5 points are important in food processing. You might need to do some extra reading and have a class discussion.

Below are guidelines to facilitate the discussion and answers.

Hygiene - it is very easy for germs and bacteria to start growing in food. Therefore, manufacturers have to take every possible precaution to ensure that every utensil, mixer, piece of equipment and specifically the workers' hands and clothing is sterile and remains that way.

Energy efficient - the extremely high cost of energy sources such as electricity, oil or diesel, makes it vital that food production uses the smallest amount of energy to 'get the job done safely'. The more money that needs to be spent on energy the smaller the profit for the company will be.

minimal wastage - manufacturers make every effort to cut down as much as possible on any and all waste. The more waste there is the less profit they make and the more they have to spend on removing and 'getting rid' of the waste.

Labour (measured as the number of working hours per ton of finished product) - manufacturers try to cut down on the amount of people that handle any given food product because that increases the cost to the company. Labour in certain countries costs more than in others which also pushes up the price of the goods.

Minimal factory shutdowns - each time the factory or operation gets shut down to clean it the factory is not making money. Manufacturers therefore try to keep every small part of their production line as clean and 'maintenance' free as possible. They even try to invent machines that are self-cleaning!

Comparing traditional and commercial food processing methods

We have learnt a lot about food processing methods in our modern lives. However, the indigenous people of southern Africa have been preserving and processing food for many generations, and still use some of their traditional methods today.

INSTRUCTIONS:

Read the following description of how beer is made in the Zulu culture.

Then answer the questions that follow.

Zulu beer making

Beer (utshwala) forms an integral part in the Zulu culture, especially at social gatherings and traditional ceremonies. Zulu beer is traditionally made by the women. To brew the beer, the women soak coarse sorghum and maize in water for one day, typically in a big drum-like imbiza pot. The following day, the broth is boiled over a fire and more dry sorghum is added to the mixture. After this, the mixture is mashed together and then allowed to cool for the rest of the day. The next day (day 3 of the brewing process), the mixture is filtered through a sieve to remove the big fibres. The sieve is made from palm fronds and the brew is poured from the big imbiza vessel into the serving vessel, iphangela, made from clay. The beer is now ready to be served. The iphangela is carried from brewery in the kraal (a semi-thatched hut which allows the smoke from the fire to escape and ensures a good supply of oxygen to ferment the mixture) to the drinking assembly. A woman scoops the beer into a drinking vessel, ukhamba (a small, round clay pot decorated with traditional patterns) using a dried gourd and presents it on her knees to the men. She will first taste the beer to show the head of the household that she has brewed the beer properly, and then hand him the ukhamba, before passing it around to the rest. The beer contains 3% alcohol and it is nutritious as it is made from plant products without modern additives or colourants.

This watertight, hand woven basket, called Ukhamba, is used to store any leftover beer. http://www.flickr.com/photos/37743612@N05/4685092625/

QUESTIONS:

What are the ingredients used to make utshwala?

Sorghum, dried sorghum, maize and water

What are the Zulu names for the three different clay pots (vessels) used in the beer making process?

Imbiza (brewing vessel), iphangela (serving vessel), ukhamba (drinking vessel)

What are these vessels made from?

Clay

Why does the brewery hut only have a semi-thatched roof and not a fully, enclosed roof?

This is because the women have to make a fire inside to boil the mixture. So they need an opening to allow the smoke to escape, and they need a supply of oxygen for the fire to burn and the fermentation process.

Use the space below to draw a flow diagram to illustrate the Zulu beer-making process. Remember to include arrows to show the direction.

For the following task, you need to do some research outside of class, using books and the internet. Find out how beer is made in a modern brewery, such as the South African Brewery in Newlands, Cape Town. In the space below, write a paragraph where you compare this modern beer-making process to the indigenous method of the Zulu people.

Food Processing Project

Now that you have a better idea of the different ways that raw food can be processed, choose one particular method that you found really interesting to further research and then process the food at the end.

After researching the method, learners are encouraged to actually carry out the food processing, either at home or in class. On a specified day when learners present their projects, they can bring the actual food product to class for others to taste.

INSTRUCTIONS:

You need to read as much as possible about your chosen method of food processing.

You will need to interview at least one person who uses this method of food processing. Before your interview you will need write down at least 10 different questions to ask this person during the interview. You need to include these questions and the person's answers in your project's presentation.

After your research and interview you need to include a few paragraphs headed: "What I learnt about food processing ... " This must be a summary of the information you learnt.

Present your findings in a visible form that you like - perhaps a poster, PowerPoint slide show or in a flip-file as a brochure. Be creative and present your information in a lively and interesting way!

Use the knowledge and understanding that you gained and process the food using this method.

You will need to make your presentation to the class. You must include all the steps you followed to process your chosen food. Bring some of your processed food to class so that you can all enjoy what everyone has made.

When you choose a processing method make sure you have food that you will be able to process using this method! If you cannot find fresh (raw) peaches to poach because it is winter then consider choosing another processing method!

Teacher note: Below is a guideline rubric to assess each learner's project.

5

4

3

2

1

Research skills

Rigorous pursuit of knowledge and understanding; information paraphrased very clearly.

Good coverage of information and new knowledge / understanding; some evidence of paraphrasing

Adequate and fairly precise knowledge gathered. Mostly copied information.

Information gathered by copying and pasting information in random without much planning.

Not much information gathered. Some information is space-filling and serves little purpose.

Interview skills

Questions and answers displays very clear understanding of processes involved and information needed.

Questions are clear and to the point though not always focused. Some answers are well structured.

At least 1/2 of questions are well structured / formulated but not always relevant and focused.

Some questions were formulated well but these are not in any particular order and do not flow one from the other.

Questions don't always pertain to the topic. Some questions are difficult to understand. Did not formulate 10 questions.

Ability to synthesise information in a summary

Summary creates a very good overview of main ideas. Clear and precise synthesis of information from research and interview.

Summary is fairly concise and contains many main ideas but often supporting ideas have been included as well making it too long.

Summary is in places a copy of the previous texts. Some main and many supportive ideas included. Incomplete.

Summary is very short and contains only a few strands of information. Imprecise and lacking.

If summary is included it is no more than one or at the most two short sentences. Incomplete and containing many misunderstandings

Referencing and bibliography

All references are noted and bibliography is complete and well presented.

Some sources acknowledged and referenced. Fairly good bibliography.

One or two sources acknowledged. Bibliography contains titles yet incomplete.

No sources referenced in text, but one or two sources were included in bibliography.

No bibliography or referencing of sources.

General impression of presentation

Well presented, neat and creative presentation. Good use of language and resources. Interactive and lively.

Fairly well presented but could be neater. Presentation was good. Fair amount of effort applied.

Some effort applied but presentation could be far more creative and interesting. Could have used resources more effectively

Presentation was generally simplistic with little use of colour, layout or creativity. At times the reader feels confused and cannot follow.

Presentation was untidy and sloppy. Information was inaccurate. Poor use of language. Very little evidence of effort applied.

Effective use of information to process food

Used knowledge and understanding gained in research and interview very effectively to plan food processing.

Fairly good understanding of food processing procedure and application in own process.

Good correlation between some aspects learnt and practical application, though not all.

Applied at least 3 theoretical concepts learnt but could not sustain this without support.

Could not correlate knowledge from research with practical application.

Appropriate choice of food to process

Excellent choice guided by research, interview and food availability.

Considered majority of constraints and made a good choice.

Choice was made difficult as did not consider all constraints.

Chose a random food that posed tremendous problems as did not consider all constraints.

Did not prepare beforehand. Chose inappropriate food.

Outcome of the food processing

Food was very well processed and looked and tasted delicious.

Some items were processed correctly and looked and tasted fine.

One or two items were successfully processed. Others 'didn't work'

Although the idea was correct the result did not work and tasted / looked unappetising.

Lack of preparation thus food processing was unsuccessful.

Demonstration of food processing

Demonstration was lively and entertaining. Audience enjoyed it very much!

Demonstration was fairly well presented yet with a few hiccups.

Very nervous presenting yet tried hard. Audience was lost in places.

Demonstration was short / incomplete. Battled to explain the process.

Tried to present / demonstrate but lacked confidence or understanding of process.

Breakdown of steps to process food

Very precise and clear breakdown of steps.

Fairly precise yet not always clearly communicated breakdown of steps.

Steps were not well ordered but could break down process in main phases.

Could only identify some of the main phases but not in logical order.

Needed much prompting to identify one or two of the main phases in the process..

TOTAL:

/50

Food is processed to make it edible, by cooking or preparing it for example.

Food is processed to make it last longer - we say to preserve it.

Food is processed to improve its nutritional value by fermenting it for example.

During processing many foods may lose some of their nutrients.

Various methods are used to process food.

Write a definition for 'food processing' that will explain what it means.

Changing raw animal or plant material into products and food that we can eat and use.

There are three main reasons why we process food. Explain what is meant by the following words in relation to food processing.

preserving

cooking / frying

fermenting

making food last longer

making food edible

increasing the nutritional value of food

Many people believe that processing food is not good for their health. List three possible drawbacks of food processing.

There are many additives added to food - preservatives, colourings, artificial sweeteners and salt, etc.

Nutrients may be lost in the process.

There is a risk of contamination from various sources.

Describe how you would preserve extra fish that you had caught while on an overnight camping trip.

clean and gut the fish; wash it in salt water and fillet the fish; sprinkle course salt and spices over it; hang it to air-dry in a well-ventilated space, away from scavengers and pesky insects.

A farmer wants to export table grapes to Australia from his farm near Worcester in the Western Cape. Suggest the best form of transport that you know of that he should use and explain why you gave him this advice.

He should pack these grapes in special boxes that will protect them and place these directly into cold rooms. A special cooling truck should fetch these boxes and take them to the airport from where they can fly to Australia in the freight planes.

Below is a table. Next to each item in column A write the degree to which the raw materials were processed.

Food

Degree of processing

mealie bread

fresh mealie washed and half-way peeled packaged in a styrofoam container

sunflower oil

Explain why many people believe that highly processed food is bad for your health.

The food processes involved in making highly processed foods destroy many nutrients. Some methods of processing add a lot of extra sugar, fats or oils.

Compare the methods of any two food processing techniques.

Here the idea is that learners use their project's information to support their explanation of the food processing methods.

Write a short paragraph summarising what you have learnt about food processing and why you think it is important in your daily life.

Learner directed answer.

Ecosystems and food webs

What is an ecosystem?

How often does it rain in a rainforest or in a desert?

Now that I know how people eat, how do animals get their food?

Why can animals only eat one type of thing - for example why won't a great white start eating kelp or why won't a tortoise hunt a dolphin?

Introducing this topic

Many of the concepts in this unit revise work done in Gr. 5 with the consequence that this unit has taken a different approach: these topics were not dealt with in depth but given a good, clear introduction to revisit and acknowledge existing knowledge and then we move to a stronger focus on environmental problems and permaculture as one of many positive solutions. If at all possible, watch the video clip on permaculture - it is fantastic and inspirational, and makes for far more positive reading than the doom-and-gloom that tends to dominate the media today.

Nothing in the world can live truly on its own. No plant or animal, and certainly no human. Living things are connected to each other, they depend on each other and on the non-living things in their environments.

In this chapter we will take a closer look at ecosystems and examine the different kinds of ecosystems that we get around the world, see how animals, plants and microorganisms depend on each other and learn about food webs and feeding relationships in an ecosystem.

Different ecosystems

ecosystem

dependent

interdependent

permafrost

An ecosystem is an area where living and nonliving things depend on each other in many different ways. An ecosystem can survive on its own without any help or products from any other sources because the living and nonliving things in the ecosystem depend on each other for their survival.

There are many different types of ecosystems on our planet:

rivers

mountains

sea and the rocky shores

ponds and wetlands

arctic and alpine tundra are in extremely cold regions close to the North and South poles. There are no trees but some shrubs and dwarf plants grow in wet, spongy soil if it is not permanently frozen (they call this permafrost).

grasslands: tropical savannas and temperate grasslands.

forests, including tropical rain forests, and forests of coniferous and/or deciduous trees in moderate climates support many kinds of herbivores and carnivores.

deserts and semi-deserts

Describing different ecosystems

INSTRUCTIONS:

Below is a table with photographs of different ecosystems. Study each photograph.

In the column next to the photo, identify the type of ecosystem.

Then write a description of the ecosystem where you identify:

some important physical features and structures, such as rivers, mountains, rocks, etc.,

the type of climate you expect where this ecosystem is found, and

the types of plants and animals you would expect to find in the ecosystem and why they might benefit from living in these conditions.

In America, grasslands are prairies and in Asia they are called steppes; in South America they call it the Pampas and in South Africa we often call it bushveld or savanna.

Ecosystem

Type and description of ecosystem

Answers: Also assess learner's descriptions in terms of the physical features of the ecosystem and how the plants and animals might benefit from these conditions.

wetland/pond: reeds, water lilies, birds, fish in the water, terrapins, etc

rocky shore: crabs, mussels, small fish, limpets, sea gulls, penguins, seaweed, etc

forest: birds, small buck (red duiker), small mammals (mice), big trees, creepers

desert: cacti, grass, other succulents, snakes, small mice, birds

river: reeds, trees, fish, birds, otters

snow-capped mountains: minimal life - sparse vegetation, mountain goats, snow leopards, rabbits, etc

savanna/grassland: grasses, a few trees, birds, small rodents, game (ie. buck, leopards, zebra, etc)

coral reef: coral, seaweed, tropical fish, turtles, dolphins, crustaceans, anemones, etc

A unique South African ecosystem

South Africa's fynbos region is unique - it produces an incredible array of plants and specifically flowers. Our national symbol, the Protea, grows wild here - and NOWHERE else in the entire world!

The King Protea, our national flower http://www.flickr.com/photos/wrathdelivery/393079740/

Typical fynbos at Cape Point Nature Reserve http://www.flickr.com/photos/graeme/4183321986/

A fire passed through this fynbos area near Kleinmond, Western Cape. A year later the indigenous fynbos had regrown but the pine trees that are not indigenous were all dead.

South Africa is famous for its fynbos - it does not grow naturally anywhere else in the world! Fynbos plants are especially adapted to survive the climatic conditions and frequent fires. The low bushes can survive the harsh windy conditions and the plants produce seeds that can very often only germinate once they had been scorched by fire.

The Fynbos biome in South Africa has a huge biodiversity in plants and animals.

Living and non-living things in ecosystems

In an ecosystem, there are certain relationships between the living things and the non-living things in a particular area.

A healthy ecosystem is one in which there is a balance between the non-living and living things. a healthy ecosystem also depends on sufficient biodiversity of plants, animals and their habitats.

We saw at the beginning of the term that plants depend on air, water and sunlight in order to make their food. Do you remember what this process is called?!

What are some of the non-living things in an ecosystem?

air, sunlight, water, soil

What does biodiversity mean?

Biodiversity refers to the variety in the species of organisms (plants and animals) in a given habitat.

Animals also depend on the non-living things in their ecosystem. All animals need to breathe (oxygen from the air around them) and they need to drink water. Some animals also use the non-living things to make their shelters. For example, ants rely on the soil and sand to build their nests in.

Assessing the balance between living and non-living things

INSTRUCTIONS:

Look at each of the following photographs of different ecosystems in which the balance between living and non-living things has become upset.

Answer the questions on each picture.

A dried river bed.

In this river ecosystem, the water has dried up due to a drought. How does this affect the biodiversity of the plants and animals in this ecosystem?

Many animals which relied on the water as their habitat would have died, such as fish, frogs, etc. In turn the birds which ate these animals would have left. Plants which relied on very moist soil would have died, such as reeds and water lilies.

However, many of these ecosystems also have animals adapted to dry seasons (fish and amphibians go dormant, elephants dig for water). Although, long periods of drought are still detrimental to these animals.

The soil has started to erode. http://www.flickr.com/photos/soilscience/5097054849/

In this photograph the soil has started to erode. Why do you think this happened?

This may be a difficult question to answer. It could be because the land was farmed and so the naturally occurring plants were removed. There are now no roots holding the soil together. When the rain comes, it washes the soil away causing erosion.

A pine tree plantation

In this man-made forest, there is not much life under the canopy of the trees. Why do you think this is so?

This is because the trees block a lot of the sunlight which plants and animals need, so they do not live there. Also, the pine trees use a lot of the water in the ground, meaning there is not much left for other plants.

As you have seen from this activity, the living things depend on the non-living things in an ecosystem. There is also a very fine balance, and if something is upset, then the ecosystem will begin to deteriorate.

The importance of water in an ecosystem

Without water life as we know it cannot exist.

Animals depend on water in their ecosystems

Water provides a habitat for many different organisms and allows plants and animals to survive and breed.

Water is a universal solvent and allows important chemical reactions to take place. It is a key ingredient for photosynthesis where plants create glucose (sugars) from sunlight, water and carbon dioxide.

Water plays an important role in plant reproduction as some seeds need to be dispersed by water. (Try and remember which seeds get dispersed by water?)

Food webs

food web

microorganism

We have now learnt what makes up an ecosystem. We now know that there are relationships between living and non-living things. In an ecosystem, plants and animals are also connected to each other due to their feeding relationships. The plants in an ecosystem are called the producers and the animals are the consumers.

Do you remember what a producer and a consumer does in an ecosystem (from Gr. 5 work but also from the photosynthesis work you started this term with)? Write an answer below.

A producer produces food through photosynthesis from sunlight, water and carbon dioxide while a consumer cannot produce its own food and therefore eats the producer or other consumers.

There are different types of consumers:

herbivores only eat plants and plant products.

carnivores only eat meat and meat products (eggs).

omnivores eat plant and animal products.

insectivores only eat ... can you guess what?

scavengers eat dead animal matter.

decomposers are microorganisms like bacteria and fungi, as well as mushrooms, that break down animal and plant material into tiny particles and recycle it into the ground ready for the plant to use.

What do you call a human herbivore?

Vegetarian

Do you remember in Gr. 5 when we looked at food chains? Here is an example of a food chain:

A simple food chain

Turn to a friend and design your own food chain consisting of four organisms. Remember a food chain always starts with plants (producers) and ends with scavengers or decomposers.

In a whole ecosystem, the feeding relationships between plants and animals are much more complex than a simple food chain.

In the above food chain, for example, the chameleon might also eat flies or butterflies, the snake does not only eat chameleons, but also lizzards and mices, and the mongoose also eats small birds and eggs.

So what is a food web?

When we put many different food chains in an ecosystem together, we get a food web.

Food webs (video) http://www.youtube.com/watch?v=YvZlooi5_kE

A food web consists of many thousands and thousands of food chains that are connected to each other.

Below is a food web in a savanna ecosystem.

A food web in a savanna

There are also different levels of consumers in an ecosystem:

Primary consumers are the herbivores which eat the plants, such as the mice and grass in this savanna food web.

Secondary consumers eat primary consumers.

Tertiary consumers eat the secondary or primary consumers.

Study the food web and identify the producers and the consumers. Distinguish between the primary, secondary and tertiary consumers. You can write your answers (in pencil in case you make a mistake) on the food web illustration.

Below is another food web consisting of plants, fish and birds. What kind of ecosystem do you think this food web describes?

A food web consisting of plants, fish and birds.

Aquatic - wetland, river, lake, pond, etc

Drawing food webs

INSTRUCTIONS:

Use the following lists of organisms in a sea and forest ecosystem to draw a food web for each ecosystem.

Sea ecosystem: phytoplankton, sea weed, zooplankton, crab, lobster (scavenger), prawn, small fish, large fish, turtle, seal, dolphin, killer whale.

Forest ecosystem: grass, small plants, seeds, beetle (herbivore), butterfly, tree frog, rabbit, mouse, seed-eating bird, insectivorous bird, snake, fox, owl.

Now that we have learned about the living and nonliving things in an ecosystem, and the relationships that exist, let's investigate an ecosystem in or near the school.

When a scientist, such as a botanist, zoologist or ecologist, goes outside to do their work and experiments, this is called "field work".

Studying an ecosystem

For this activity, the teacher can identify some possible areas in or near the school before the lesson. Then when it comes to the lesson, time is not wasted finding appropriate spots. learners can either all study the same spot, or there can be several spots covering different ecosystems. Encourage learners to take notes on their scrap paper and clipboards whilst they are outside to practise their observation and note-taking skills.

MATERIALS:

8 sticks

string (about 30 m)

clipboard

scrap paper

pen and pencil

reference books for identifying species names

INSTRUCTIONS:

You will work in groups for this activity.

Go outside with your teacher and identify an ecosystem in your school grounds, or near to the school which you can study

You will need to mark out the area with the sticks and string using the quadrant method.

Look at the picture below to get an idea of how to set up your quadrants.

The area must be about 5m x 5m.

Once you have marked out the square, divide it up into 4 smaller squares with the string so that you have a quadrant with 4 squares as shown in the picture.

A 5m x 5m quadrant

When marking out your ecosystem to study, be careful not to damage any of the plants and animals that are there as this is what you will be studying.

For each of the 4 quadrants in your ecosystem, count the number of different species of plants and animals.

See if you can identify the names of the different plant and animal species using reference books. Fill this out in the table below when you get back to class.

Study the non-living things in your ecosystem. For example, what type of soil is present? Are there any rocks? Is there perhaps a stream running through your ecosystem? What is the sunlight like, shady or full sun? Are there any animal shelters present? Make notes about this as you will have to answer questions when you get back to class.

QUESTIONS:

What type of ecosystem are you studying?

Activity-dependent (ie. grass ecosystem, stream/river ecosystem, forest ecosystem, etc)

What is the total area of your square?

Dependent on learner's square, but if the square had 5m sides, then the area is 5mx5m = 25m.

Fill out the table below for each quadrant:

Quadrant 1

Quadrant 2

Quadrant 3

Quadrant 4

Number of plant species

Number of animal species

Total organisms in each quadrant

What is the average number of plant species in the whole square? (Hint: To work out the average, add up the number of plant species for each quadrant and divide by the number of quadrant).

What is the average number of animal species?

What is the average number of total organisms in your ecosystem?

What is the number of organisms per unit of area? This is quite tricky - your teacher might need to help you!

To work out number of organisms per unit area, divide the total number of organisms by the total area of the square. The answer will be in number of organisms/m2. Do this calculation on the board for your learners to see and then repeat with their own numbers.

Fill in the names of 3 species of plants and 3 species of animals that you identified in the table below. Do a simple drawing of each organism and write a short description of each species.

Names of species

Drawing

Description

Plant species:

1:

2:

3:

Animal species:

1:

2:

3:

Write a description of the non-living things in your ecosystem. Explain the availability of food for the animals, the water availability, the type of soil (sandy or rich organic, soil, for example) the amount of sunlight (shady or full sun for example), and describe if there are any natural shelters for animals.

Encourage learners to investigate and explain some possible reasons for observed phenomena, for example, presence of a particular insect, colour of soil, presence of a certain type of plant, etc.

Your ecosystem will contain animals and plants which are interdependent and they are connected by their feeding relationships. Use the space below to draw a food web for your ecosystem.

Ecosystems are often destroyed due to the impact of humans or other environmental disasters, such as a flood or drought. Identify some possible threat to your ecosystem and write about them below and why they could destroy your ecosystem.

Brainstorm possible ways to prevent these threats to your ecosystem from destroying it. Record your ideas below.

There are different ecosystems where living and nonliving things depend on each other.

Living and nonliving things share an ecosystem.

Food webs show how plants and animals are connected by their feeding relationship.

Plants are producers of their own food.

Animals are consumers and eat plants or other animals.

Microorganisms are decomposers and break down dead plant and animal material and return the nutrients to the soil.

Provide a definition for an ecosystem.

An ecosystem is an area where living and non-living things depend on each other in many different ways. It consists of all the organisms and their habitats in a given area.

Why do you think the feeding relationships between plants and animals in an ecosystem is called a food web?

This is because when you draw all the links in between all the organisms, it looks like a spider's web as each organism has multiple relationships with other organisms.

What is the term given to animals which break down dead plant and animal material?

Decomposers (microorganisms)

Read this blog entry made by a Gr. 6 pupil in Limpopo province reporting on their environment.

"I live in the Waterberg area in north Limpopo province. This is the first area in South Africa to be named a biosphere reserve. During the Stone Age indigenous people lived in this area. They brought in cattle that overgrazed the grasslands and caused a terrible outbreak of tsetse flies. Then in the 1900s Dutch farmers brought in more cattle. All the cattle, goats and sheep of the Dutch farmers and the indigenous people almost destroyed the natural bushveld vegetation.

Luckily the people realised the problems in time and started to reintroduce and protect original species of animals and plants to the area. White rhino, giraffe, hippopotamuses and different species of antelope and smaller buck returned. Ecotourism is now very popular and farmers try really hard to stop soil erosion, and to introduce original grass species. Farmers also started to take away fences between their farms to allow animals to walk free."

Described what happened to the land when all the cattle, sheep and goats were grazing on it.

The animals over-grazed the land which means most of the natural vegetation was eaten and did not have enough time to regenerate, so the soil was left without protection and started to erode.

Explain what happened to the original, indigenous animals that lived on the land after the cattle farmers arrived?

Because the original animals could no longer find the natural vegetation they were used to, they either starved or moved out of the area.

Can you predict what would have happened if the people did not change the way they used the land?

The land would become a barren and desolate place with no vegetation left, which means very little rain will also fall there. The precious topsoil would erode and the landscape would become a desert.

What factors did they have to change to protect and conserve their land?

They removed the many cattle herds that were over-grazing and replaced them with the original animals that used to live in that area. They also replanted the natural, original plant species that grew well in that area to provide food for the animals. They then advertised this area as a eco-friendly tourist attraction and made lots of money from tourists rather than from destroying the countryside.

If the farmers instead of removing the cattle and goats, rather planted crops on the land, what do you think would have eventually happened?

The soil would probably not have sustained the crops for many years, so the farmers would spray lots of fertilizers and probably poisonous pest controls which would have further destroyed the environment.

What choices do you need to make or what do you need to change or improve in your community to stop similar types of environmental destruction from happening there?

This is context specific but learners need to show evaluation and creative problem solving skills to come up with good suggestions to save their own communities.

Solids, liquids and gases

How are the 3 states of matter different from each other?

How can we draw pictures of the 3 different states of matter, that show how the particles in the matter behave?

When matter changes from one state to another, do the particles themselves change, or only their behaviour?

What is needed to make matter change from one state to another and back again?

Arrangement of particles

Only 1.75 hours is allocated to this section in CAPS which is quite short. If you do not have time to do all the activities, then leave out the third activity on the states of water.

We have learnt that matter can exist in 3 different states: solids, liquids and gases. All the materials around us are in one or more of these three states. For example, you have all three states in your body! There is bone in your skeleton. There is water in your blood. There is air in your lungs. We have also learnt that each of the states (solids, liquids and gases) has unique properties:

state (of matter)

particle

vacuum

Solids keep their shape.

Liquids flow and take the shape of their container. They fill up a container from the bottom up to a certain level. They take up a fixed amount of space in the container.

Gases also flow and take the shape of their container. They always fill up the whole space of the container and will escape if the container is open.

We know when we have a solid or a liquid. It is easy to see a solid or a liquid. We cannot normally see gases. We can still check that gases are present by seeing their effects.

Why do solids keep their shape but liquids and gases flow? Why does a liquid stay inside an open container (unless it is poured out), but a gas escapes?

We have to look deep inside each state for the answers to these questions. We will have to use our imaginations like never before!

Did you know that all matter is actually made up of very small particles? These particles are called atoms and molecules, and we will learn more about them much later. For now, we are going to use the term particle to describe the smallest 'building blocks' that matter is made of.

The particles that matter is made of are very, very small. Much, much smaller than a tiny grain of sand. Much, much smaller even than a speck of dust! Do you have any idea how small that is?

Most people find it very hard to think about, so do not worry, we will go through it slowly.

The particles that matter is made of are much too small to see with the naked eye. They are even too small to see with a strong microscope. So how do we know they exist? Scientists, with special microscopes and other special scientific instruments, have collected evidence that they exist. It is now a well-known and accepted fact that all matter is made up of particles.

Particles of Matter (video) http://www.youtube.com/watch?v=UnBoQe2rsgo

The particles in a solid

Let's imagine that we can shrink ourselves down to the size of such a 'matter particle'. What would we see if we could look around inside a solid?

We would see the particles in the solid are packed tightly together. This explains why solids cannot be squeezed into a smaller shape - solids cannot becompressed.

We would also see that the particles in the solid have fixed positions; they cannot move from their positions. This explains why solids keep their shape.

The particles in a solid.

The particles in a liquid

If we could shrink ourselves down to the size of a 'matter particle', and we could look around inside a liquid, what would we see?

We would see that the particles in the liquid are also very close together. Like solids, liquids cannot be compressed either.

Unlike solids, the particles in a liquid do not have fixed positions. They are always moving around. This explains why liquids flow, to take the shape of their container.

The particles in a liquid.

Even when it looks like the water inside a glass is still, the water particles are constantly moving!

The particles in a gas

If we could shrink ourselves down to the size of a 'matter particle', and we could look around inside a gas, what would we see?

We would see that the particles in the gas are far apart. The spaces between the particles are huge compared to the size of the particles themselves. These spaces are empty! We call this a vacuum. This explains why gases can be compressed - they can be squeezed into a smaller shape by pushing them closer together. We can make the spaces between them smaller.

The "space" between the particles is empty. It is a vacuum. It is not filled with "air" which is actually a mixture of other gases. If learners ask "There can't just be nothing?", that is just the answer - there is nothing. There is empty space between the particles, just as in outer Space, there is a vacuum. A vacuum is a space entirely devoid of matter. Note that the space between atoms, regardless of the state of matter, or even inside atoms, is vacuum as well. Even the spaces between particles (atoms) in a solid is a vacuum, but these spaces are just much, much smaller compared to the spaces in a gas.

The particles of a gas are always moving freely. If they are in a closed container, they will spread out to fill the whole container. If they are in an open container they will not stay inside for long. They will flow out of the container, and disperse (disperse means to spread out over an area or space.)

The particles in a gas

Acting out the states of matter (video) http://www.youtube.com/watch?v=I9xB4hhWvXY

Pretending to be particles!

This activity would be best performed in a big space, possibly outside on a field. Divide the class into groups. Each group should have enough learners to be able to do the activity meaningfully (ie. 3 is too little in a group, but 8-10 would be ideal). Each group will pretend to be all 3 states so that they get an idea of the difference. There are two key issues here: the submicroscopic behavior of individual particles and the bulk or aggregate effect.

This activity should also be used to revise the role that adding and removing of energy play in changing states. Change of state was dealt with in Gr. 4 and Gr. 5, but not in Gr. 6, so this activity does present an opportunity to revise the concept. An idea is to go through each of the states first so that they can all have a chance being a particle in a different state and you can correct their movements/behaviour. And once they have done this, you can then do the activity again and they can then do the transitions between the states. This emphasises that it is the same particles in each state, just their behaviour changes as energy is removed or added.

NB. Another aspect to be aware of when doing this activity, is that this activity may introduce the idea that the particles make decisions. This need not be addressed with the learners, but it is important to be aware of the possible misconceptions which could be introduced with any metaphors used in science education.

In this activity we are going to pretend to be particles! We are going to behave in the same way that particles do in the 3 different states of matter.

Your teacher will divide the class into groups and then we will go through the different states pretending to be the particles!

INSTRUCTIONS:

Solid:

Since you are the particles in a solid, you should sit or stand as closely as possible to (touching) each other, in neat rows, and move your body, but without moving your feet.

The particles must bump around independently, not sway in unison (as happens once or twice in the video).

If we wanted to move these particles from their fixed positions, what should we give them?

The particles should be given energy.

If we wanted these particles to move into fixed positions again and not move around, what must we take away from them?

We should take away some of their energy.

When you get learners to change state from a solid to a liquid, it is VERY important to stress the point that the particles remain the same on the solid, liquid or gas state - it is just their behaviour which changes. A common misconception is that solids have particles that are solid; liquids, particles that are liquid, and gases have particles that are gases. This is not true as the particles are the same in each state. By getting learners to act out each state they will see that it is the same group of people in each state - just their behaviour and movement changes.

Liquid:

Now let's pretend to be the particles in a liquid. Stay in the same group.

Since you are the particles in liquid, you should now move around but stay in contact with each other all the time.

If we wanted to move these particles further away from each other, what should we give them?

The particles should be given energy.

If we wanted these particles to move into fixed positions and not move around, what must we take away from them?

We should take away some of their energy.

Teacher note: For the gas state, you could provide each group with a "container" that they have to remain within, such as placing a piece of string out on the ground in a square.

Gas:

Now let's pretend to be the particles in a liquid. Stay in the same group.

Since you are the particles in gas, you should now move around and be as far from each other as possible.

If you should come into contact, you must move away from each other immediately.

If we wanted these particles to move more slowly and come closer to each other, what should we take away from them?

We should take away some of their energy.

If we wanted these particles to move into fixed positions and not move around, what must we take away from them?

We should take away even more of their energy.

How do we decide whether a material is a solid, a liquid or a gas? The next activity will help us answer that question. We are going to think about some everyday materials. We will use our skills of observation to decide whether they are liquids, solids or gases.

Can you remember what your skills of observation are?

Skills of observation are the skills that involve our senses. In today's activity we will be looking at materials and thinking about how their particles might be behaving.

Once we have decided whether a material is a solid, a liquid or a gas, we can make some predictions about the behaviour of the particles in each material. For this we will need our imagination, as particles are much too small to see with the naked eye.

Solids, liquids and gas particles (video) http://www.youtube.com/watch?v=guoU_cuR8EE&feature=related

In the video on "Solids, liquids and gases", forces are mentioned (attraction and repulsion), but have not been dealt with yet at this stage. Be aware too that the animation of the two molecules in the solid chocolate as it melts better reflects the situation in a transition to the gaseous state (they bump around in a rectangular box). But this video still provides some sort of animation of a difficult concept.

The 3 states of matter in everyday life

Here you should try to make the link between the observable (macroscopic) and imagined (submicroscopic) worlds that is so important in conceptual development for science. What we see (what we observe on a macroscopic level) tells us more about what is occurring on a submicroscopic level. For instance, the fact that a solid keeps its shape tells us that the molecules in the solid stay in their respective places. Conversely, a submicroscopic understanding helps us to explain what we observe on a macroscopic level. For instance, the knowledge that there are large empty spaces between the particles of a gas helps to explain why two gases mix so easily (a process called diffusion). Remember that this empty space is just that - there is a vacuum between the particles. Also, diffusion occurs relatively easily in miscible liquids. It's not just spaces but also particle speed and freedom to change position that play roles here.

INSTRUCTIONS:

The table below contains a list of containers:

1. Say what material is usually kept in each container. Write your answers in the middle column.

2. Say whether the material is a solid, a liquid or a gas. Write your answers in the column on the right.

Container

What material is inside?

Is this material a solid, liquid or gas?

Air (actually helium gas as they are floating)

Gas

Water, and if boiling then steam (which escapes from the container)

Liquid inside the kettle, steam is a gas

Ice

Solid

Air

Gas

Milk

Liquid

Oil

Liquid

NB. In the above example of a kettle it is very important to take note of what steam is. Steam IS NOT the suspension of very fine water droplets which you are able to see coming out of the kettle. This is actually water in the liquid state, but the droplets are so fine that they are suspended in the air. This misconception arises as in common language, it is often used to refer to the visible mist of water droplets formed as water vapour condenses in the presence of cooler air. People talk about the steam coming out of the kettle or off a mug of coffee which you can see. This is incorrect in terms of physics and chemistry as true steam is invisible. Steam is rather the transparent mixture of gaseous water and air, which is not visible. Steam is the technical term for water vapour, the gaseous phase of water, which is formed when water boils. Water vapour cannot be seen.

In the table below there are 3 pictures.

1. Look at how the particles are arranged in each picture and say whether it represents a solid, a liquid or a gas. Write your answer in the middle column.

2. For each picture, choose 2 examples from the previous table and write them in the column on the right.

Pictures of particles

Solid, liquid or gas?

Examples of materials

Gas

Air, steam

Solid

Ice, ice cream

Liquid

Water, milk, oil

Draw a picture of the particles inside each of the following examples:

1. bar of soap

2. cup of tea

3. balloon

In the previous activities we learnt about the behaviour of the particles inside materials. In the next activity we will learn about the particles in different states of the same material.

In the first activity, the learners in your class acted out the behaviour of particles in a solid, liquid and gas. When the 'liquid' learners changed to 'solid' learners, did the learners themselves change as they changed from solid to liquid?

(Did John, Sarah and Thandi change into different people?) No, they did not change.

Did they behave differently?

Yes.

In what ways did their behaviour change?

They slowed down. They moved into fixed positions and stayed in those positions.

We know that materials can change from one state to another and back again. Can you think of an example of this?

Ice melting and then freezing again.

What happens to the particles inside a material when it changes from one state to another? The next activity will help us to answer that question.

The states of water

The objective of this extension activity is to establish that a change in state does not change the characteristics of the particles of a material, they only change the behaviour of the particles. If you cannot watch the video, then use the images supplied below. Although "State Changes" is not specified for Gr. 6 in CAPS, if you have time, it could be a good idea to do this again and refresh what learners did in Gr. 4 as they might not remember and these are important concepts for Physical Science in the higher grades.

INSTRUCTIONS:

In this activity we will watch a video about water in 3 different states: solid, liquid and gas.

Follow the link below and watch the video, then answer the questions that follow. http://www.youtube.com/watch?v=s-KvoVzukHo&feature=share&list=PLBD54C6BCA947A5E4

If you cannot watch the video, do not worry! Study the picture below instead.

A fun website with activities about materials http://www.bbc.co.uk/schools/ks2bitesize/science/materials

QUESTIONS:

What do we call the solid state of water?

Ice

What do we call the liquid state of water?

Water

What do we call the gas state of water?

Water vapour or steam

What do we call the process of ice changing to liquid water?

Melting

What do we call the process of liquid water changing to ice?

Freezing

What do we call the process of liquid water changing to water vapour (steam)?

Evaporation

What do we call the process when steam (water vapour) changes to water?

Condensation

Do the particles in the ice change when the ice melts?

No, the particles stay the same. They are still water particles.

If ice and liquid water have the same particles, why do ice and liquid water have different properties? (Ice is solid and water is liquid.)

The particles of water behave differently in ice and in water. In ice the particles are packed and stay in position. In liquid water the particles are still very close together but they can move around.

How can the water particles in ice be made to move freely? (Think of the 'solid' learners. What did we give them to make them move?)

We should give the particles some energy.

Matter can exist as 3 states, namely solids, liquids and gases.

The particles in solids are closely packed and have fixed positions.

The particles in liquids are also closely packed but they can move around each other.

The particles in gases have large empty spaces between them.

How can we change water to steam?

We must heat the water (give it more energy).

How can we change water to ice?

We must make it cold (take away some of its energy).

How are the particles arranged in a solid?

The particles in a solid are tightly packed into fixed positions.

How do the particles in a gas behave?

The particles in a gas are moving around all the time, and they are far apart. They fill all the space available to them.

Below are 3 images of water in the different states of matter, and 3 images of the arrangement of the particles. Match the image of water with the arrangement of particles by drawing lines between them, to pair them up.

Mixtures

What is a mixture?

When is a mixture also a solution?

How can mixtures be separated into different materials?

Mixtures of materials

What is a mixture? A mixture is two or more different materials that have been mixed together.

In some mixtures, the different materials are still clearly visible after mixing. A mixture of peanuts and raisins would be an example of such a mixture. How would we separate the peanuts and the raisins? Well, we could simply pick the raisins out of the peanuts!

A mixture of peanuts and raisins

Can you think of other mixtures in which the different materials are still clearly visible after mixing? Look at the pictures below for some ideas.

A mixture of different coloured jelly beans

A mixture of different fruits in a fruit salad

A mixture of swans and ducks on a lake

A mixture of red, green, yellow and orange sweet peppers

A mixture of pink, yellow and white flowers

A mixture of different shells from the beach

In other mixtures, the materials are mixed so thoroughly that it seems one material has 'disappeared' into the other. Such mixtures are called solutions. We will learn more about solutions shortly.

Making mixtures

First, we will have some fun making mixtures.

Mixing solids

MATERIALS:

500g bag of barley (beans or lentils will also do)

500g bag of rice

Small packet of sugar

Clean sand (from the beach or from a building site)

Plastic spoons for scooping

Small yoghurt tubs or paper cups for mixing

Sieve (the type used for sieving flour)

You need a sieve (or strainer) that is coarse enough to let all the sugar through. A suggestion is to sieve the sugar first. Whatever passes through the sieve can be used in class.

INSTRUCTIONS (Part 1):

Place 10 scoops of barley in the mixing tub.

Place 10 scoops of rice in the mixing tub.

Stir the barley and rice until they are mixed.

Answer the questions below.

QUESTIONS:

Can you still see the individual rice and barley grains?

Yes.

Draw a picture of the mixture.

Separate the mixture into a pile of rice grains and a pile of barley grains. Write a sentence to explain how you separated the mixture.

The learners may answer: 'I picked the barley grains out of the rice' or 'I picked the rice grains out of the barley'.

Did the barley and rice grains change in any way, or do they still look the same as before they were mixed?

The grains still look the same.

INSTRUCTIONS (Part 2):

Place 10 scoops of rice in the mixing tub.

Place 10 scoops of sugar in the mixing tub.

Stir the sugar and rice until they are mixed.

Answer the questions below.

QUESTIONS:

Can you still see the individual rice and sugar grains?

Yes.

Draw a picture of the mixture.

Separate the mixture into a pile of rice grains and a pile of sugar grains. Write a sentence to explain how you separated the mixture.

The learners may answer: 'I picked the rice grains out of the sugar'.

Can you think of a quick way to separate the mixture, using a sieve? Describe what you would do to separate the mixture. Describe what would happen to the mixture.

I would put the mixture in the sieve. The sugar grains will fall through the sieve and the rice grains will stay behind.

Did the sugar and rice grains change in any way, or do they still look the same as before they were mixed?

The grains still look the same.

INSTRUCTIONS (Part 3):

Teacher note: This part of the activity needs to be planned-for by the teacher. The sand and sugar must be of the same average grain size and should be sieved in advance to ensure this is so. The impact of the uselessness of sieving will be partially or totally lost otherwise.

Place 10 scoops of sand in the mixing tub.

Place 10 scoops of sugar in the mixing tub.

Stir the sugar and sand until they are mixed.

Answer the questions below.

QUESTIONS:

Draw a picture of the mixture.

Can you separate the mixture into a pile of sand grains and a pile of sugar grains? How long would it take if you picked the sand grains out of the sugar one by one?

The learners may answer: 'It would be possible but it would take a very long time.'

Do you think that it would be possible to separate the mixture using a sieve? Why do you think so?

It would not be possible to separate the mixture with the sieve, because the sugar grains and the sand grains are both small enough to fall through the sieve.

In the previous activity we mixed solid materials with different sized grains and learnt that:

when the grains are large enough, we can separate them by hand; and

when the two materials have grains of different sizes they can be separated by sieving.

In the next activity we will explore mixtures of solids and liquids.

Mixing a solid and a liquid

MATERIALS:

clean sand (from the beach or from a building site)

plastic spoons for scooping

small yoghurt tubs or paper cups for mixing

sieve (the type used for sieving flour)

kitchen towel or paper towel

INSTRUCTIONS:

Place 5 scoops of sand in the mixing tub.

Pour water into the mixing tub until it is half-full.

Stir the sand and water until they are mixed.

Answer the questions below.

QUESTIONS:

Can you still see the individual sand grains?

Yes.

Draw a picture of the mixture.

Can you separate the mixture into a pile of sand grains and water?. How long would it take if you picked the sand grains out of the water one by one?

The learners may answer: 'It would be possible but it would take a very long time'.

Would it be possible to separate the sand from the water using the sieve? Say why or why not.

No, it would not be possible, because the grains and the water would both pass through the sieve.

Would it be possible to separate the sand from the water using the paper towel? If you think it would be possible, explain what you would do.

Yes, it would be possible. I would pour the mixture through the towel. The sand will stay behind on the towel, while the water will pass through it.

Do you think it would be possible to separate sugar and water in the same way (by filtering the mixture through a towel)? Say why or why not.

I think it would not be possible because the sugar will dissolve in the water and also pass through the towel.

In the previous activity we mixed a solid material (sand) with a liquid (water) and learnt that sometimes a mixture of liquid and solid can be separated by filtering. In the activity the towel was used as a filter.

Is it possible to mix liquids? Can you think of examples of mixtures of liquids? Look at the picture below for some ideas.

Juice is a mixture of liquids. http://www.flickr.com/photos/horiavarlan/4268285083/

Let's look at some liquids which are not so easy to mix together.

Mixing liquids

MATERIALS:

water

cooking oil

plastic spoons for scooping

small glass or transparent plastic cup for mixing

INSTRUCTIONS:

Place 10 scoops of water in the mixing tub.

Place 10 scoops of cooking oil in the mixing tub.

Stir the oil and water until they are mixed.

Let the mixture stand for a few minutes, then answer the questions below.

QUESTIONS:

Did the liquids mix? Describe what the mixture looks like.

The two liquids did not mix. There are two liquid layers.

Draw a picture of the mixture.

Do you think it would be possible to scoop all the oil out of the water? How long do you think it would take?

The learners may answer: 'It would be possible to scoop out some of the oil but it would take a very long time. I don't think it would be possible to get all the oil out of the water'.

Would it be possible to separate the liquids using a sieve or a filter? Say why or why not.

No, it would not be possible, because the oil and the water would both pass through the sieve and the filter.

Can you think of another way to separate the mixture into oil and water? If you think it would be possible, explain what you would do.

Learners may suggest pouring (decanting) the oil from the water.

Do you think it would be possible to separate a mixture of juice and water using any of the methods that we have used so far (hand-separating, sieving, filtering or decanting)? Say why or why not.

I don't think it will be possible because the juice and water will be mixed too thoroughly.

The real reason is that the juice will be dissolved in the water, which means the substances are mixed on a level of individual particles, but learners may not be able to put this into words yet.

In the previous activity we mixed two liquids (water and oil) and learned that sometimes a mixture of two liquids can be separated by decanting.

Separating mixtures

In the next section we will summarise all the different ways of separating mixtures. We have made different mixtures and tried to separate them using a variety of methods. In this section we will revise all these separation methods.

Separating mixtures

INSTRUCTIONS (Part 1)

The table below contains pictures of mixtures.

For each of the mixtures in the table, write which materials it is made up of in the middle column.

Write how you would separate the mixture in the column on the right.

Picture of mixture

Materials in the mixture

How the mixture could be separated

Peanuts and raisins

Pick the raisins out of the mixture. The peanuts will remain.

Spaghetti and meatballs

Pick the spaghetti out of the sauce, which will remain behind.

Peach, plum, banana and berries

Pick out the berries, followed by the banana pieces, etc. until all the ingredients have been separated.

Boys and girls

Tell the boys to stand on one side of the class and the girls to stand on the other side.

INSTRUCTIONS (Part 2)

The table below contains descriptions of mixtures.

For each of the mixtures in the table, write which states it is made of in the middle column (solid, liquid or gas).

Write how you would separate the mixture in the column on the right.

Description of mixture

States in the mixture

How the mixture could be separated

Water and oil

Liquid and liquid

Decant the oil off the top.

Water and sand

Liquid and solid

Decant the water off the sand, or filter the mixture.

Sugar and rice

Solid and solid

Pick the rice out of the sugar, or sieve the mixture through a sieve with holes that are small enough to let the sugar through but not the rice grains.

It is possible to mix materials in many different combinations. In a mixture, the materials that have been mixed do not change. They keep their individual properties. Sometimes it is possible to separate a mixture into the individual materials again.

A mixture consists of two or more different materials mixed together.

Sometimes mixtures can be separated into the individual materials again.

Some of the ways in which mixtures can be separated are: sieving, filtering, hand sorting, and settling followed by decanting.

When a material changes from a solid to a liquid, the process is called melting.

When a material forms a solution in another material, the process is called dissolving.

Melting and dissolving are two different processes.

What is a mixture?

A mixture is made when we mix two or more materials together.

List six different ways in which solids, liquids and gases can be combined to form mixtures.

Combine a solid with a solid.

Combine a solid with a liquid.

Combine a solid with a gas.

Combine a liquid with a liquid.

Combine a liquid with a gas.

Combine a gas with a gas.

Did you know that the air we breathe is actually a mixture of many gases? The pie chart below shows all the different gases in clean air.

Use the information in the pie chart and make a list of all the gases that are found in clean air.

Which gas is the most abundant in air? (Which gas is found in the largest amount?) What percentage of this gas is present in clean air?

What percentage of oxygen is present in air?

If you had 5000 air particles, how many of these particles would be oxygen particles?

Nitrogen, oxygen, argon, carbon dioxide, and other gases.

Nitrogen, 78%.

20.9%

20.9% of 5000 particles are oxygen particles.

Therefore, no of oxygen particles = 20.9 % of 5000

= (20.9 / 100) x 5000

= 1045 oxygen particles.

Solutions as special mixtures

When is a mixture also a solution?

Do all substances dissolve in water?

Is there a limit to how much of a substance can be dissolved in a given amount of water?

How can the components of a solution be separated?

The important message to convey in this section is that solutions ARE mixtures, albeit of a special type. The word mixture is used to describe any combination of two or more substances. A mixture can only be a solution if the particles (and here we are referring to the smallest possible particles, namely molecules) of the two substances are separate from each other and mingle freely with each other. Solutions are mixtures even at the level of molecules (or other fundamental particles).

The CAPS document includes the following two statements that are somewhat problematic:

~ when substances dissolve, solute particles become dispersed in the spaces between the solvent particles

~ a solution becomes saturated when enough solid solute has been added to fill up all the spaces in the solvent

The use of the following alternative statements is recommended:

~ when substances dissolve, solute particles become dispersed (spread) throughout the solvent particles

~ a solution is saturated when the maximum amount of solute has been dissolved in the solvent

The important idea to convey is that the particles of solute and solvent are closely mixed, in other words they are mixed on the level of atoms and molecules (particles is the preferred term here for learners at this level of development).

One possible challenge with this chapter and the one following (Dissolving) is that the concepts (solution, dissolving, soluble vs insoluble etc.) are almost inextricably linked, which makes it difficult to explain one concept without using words that are only explained in a later section. For instance, it is really difficult to explain the concept of a solute dispersing into a solvent without using the word dissolve (which is covered conceptually in Solutions, but is only named much later in the chapter Dissolving). The word dissolve will be introduced in this chapter, but used sparingly and only towards the end, so as to sensitise learners to its use, and the way in which the concept links with others in this chapter.

Solutions

Take note of the following definitions of the new words.

Solution: A homogeneous mixture of two or more substances, which may be solids, liquids, gases, or a combination of these.

Solvent: A substance in which other substances can dissolve.

Solute: A substance that dissolves.

In the last chapter we looked at mixtures. We are now going to look at a special case of mixtures, which are called solutions.

When is a mixture also a solution?

When two substances are mixed it will be possible to still see each substance in the mixture. Is sugar and sand a mixture? Yes!

solution

solvent

solute

A solution is a special type of mixture. What makes a solution so special? When is a mixture also a solution?

Often, the best way to answer a question is to ask it in a different way: When is a mixture NOT a solution?

In the next activity we are going to make a few mixtures and then decide which of them are solutions, and which of them are not. That should help us find the answer to the question: When is a mixture also a solution?

When is a mixture also a solution?

In this activity we are going to mix substances with water to see which ones make solutions.

How do you think will we know when a substance has made a solution with the water?

It will look as if it has disappeared. We will not be able to see the particles of the substance in the water.

MATERIALS:

small quantities of the following substances:

sugar

salt

sand

oil

vinegar

flour

copper sulfate

tap water

clean yoghurt tubs (small)

plastic spoons for scooping and stirring

The accepted spelling is 'sulfate' but very few people are aware of this, and most textbooks still use the old spelling 'sulphate'. When working with copper sulfate, as with most chemicals, safety precautions must be adhered to, such as wearing safety goggles and avoiding contact with the skin, eyes and nasal passages. This is a good opportunity to discuss safety precautions in general when doing science investigations, including wearing protective clothing (lab coats, goggles, gloves), as well as acting cautiously and carefully when around chemicals, and especially not drinking or inhaling any substances.

INSTRUCTIONS:

Half-fill a yoghurt cup with tap water.

Place one small scoop of sugar in the water and stir it well.

Look at the mixture and discuss what it looks like.

At the top of the table below, a few possible observations are given. Choose the one that is the best description for what you observed, by making a cross in the matching column. (You may also choose more than one column.) The first substance (sugar) has been filled in to show you what you should do.

Once you have recorded your observation, you can empty the yoghurt tub.

Repeat steps 1 - 4 until you have tested all the substances on the list.

Table: Mixing substances with water

Observations

Substance

It looks as though none of the substance has disappeared

It looks as if all or most of the substance has disappeared

sugar

X

salt

X

sand

X

oil

X

vinegar

X

copper sulfate

X

QUESTIONS:

Which of the substances seemed to disappear when they were mixed with the water?

Sugar, salt, vinegar and copper sulfate

Which of the substances in this activity did NOT form solutions with water? (Hint: which ones did not look as if they 'disappeared' into the water?)

Sand and oil

What is a solution?

When two substances make a solution, it will look as if the one substance has disappeared into the other:

The substance that looks as if it has disappeared is called the solute.

The substance that we can still see is called the solvent.

The solvent and solute together are called the solution.

The definitions provided here for solute and solvent may be a suitable distinction at this level for learners, but in general the distinction is not so clear. We tend to call the one there is more of the solvent, for example, brass is zinc dissolved in copper, and air is oxygen and other gasses dissolved in nitrogen.

Is sugar and sand a solution? (You may want to page back to Part 3 of the activity Mixing solids to remind yourself.)

No, because if we look carefully we can still see the individual sugar and sand grains.

Teacher note: One way to explain this would be as follows: If we could shrink ourselves down to the size of molecules (or 'particles', to use the language at this level) we would see clumps of sugar and sand, even if the sugar and sand crystals are really small.

Which mixtures are solutions?

In this activity we will use our observations from the previous activity (When is a mixture also a solution?) to decide which of the mixtures we made were solutions.

QUESTIONS:

In the activity When is a mixture also a solution?, we mixed different substances with water. We saw that some of the substances looked as if they had disappeared in the water.

What name do we give to the substance that looks as if it has disappeared?

Solute

What name do we give to the substance that we can still see?

Solvent

What name do we give to these mixtures?

These mixtures are solutions

Complete the table using the information about the sugar - water mixture as an example.

Mixture

Is the mixture a solution after stirring? (Yes or No)

Sugar and water

Yes

Salt and water

Yes

Sand and water

No

Oil and water

No

Vinegar and water

Yes

Copper sulfate and water

Yes

In the activity above, we mixed different substances with water.

Which substance is the solvent in all the mixtures?

Water

From the mixtures above, choose an example of a solution that consists of a solid solute and a liquid solvent.

Any one of the following examples: Sugar in water, salt in water or copper sulfate in water.

From the mixtures above, choose an example of a solution that consists of a liquid solute and a liquid solvent.

Vinegar and water

From the mixtures above, choose an example of a mixture of two liquids that is NOT a solution.

Oil and water

We know that science is not magic, and that it is not possible for something to disappear!

How do we explain the observation that one substance (the solute) 'disappears' into the other (the solvent)?

In the next activity we will look more closely at a solution, in order to understand how it is possible for the solute to look as if it disappears into the solvent.

To emphasise the logic so far, we make observations of things around us and we try to explain them using the models we develop. The learners need to get the message that the particle view is not only a description of a reality we cannot directly observe, but also a tool to explain things that we can observe.

What is a solution?

MATERIALS:

copper sulfate crystals

tap water

clear container, such as a glass beaker or test tube (a water glass will also do)

plastic spoon for scooping and stirring

INSTRUCTIONS:

Look at the copper sulfate crystals and the water. Write one sentence to describe each substance in the table below.

Mix one small scoop of the copper sulfate with enough water to dissolve it completely (half a cup of water should be enough). Let it stand for a few minutes until it clears.

Teacher note: ensure that all of the copper sulfate has dissolved, or learners will be confused by some of the results of this activity.

Look at the copper sulfate solution and write a sentence to describe it in the table below. Save it for answering the questions that follow.

Table: Description of a copper sulfate solution in water

Substance or mixture

Description (what it looks like)

Water

The water is a clear, colourless liquid.

Copper sulfate crystals

The copper sulfate is a blue solid.

Copper sulfate solution

The solution is a clear, blue liquid.

QUESTIONS:

How water mixes with a solute to make a solution (video) http://youtu.be/EBfGcTAJF4o

Look at the solution. How can you tell that there is copper sulfate in the water? Another way to ask this question would be: What evidence do you have that there is copper sulfate in the water?

The water is blue. The water is the same colour as the copper sulfate crystals.

Can you see any copper sulfate crystals moving about in the water?

No.

Explain your answer to question 2.

The crystals separated into their individual particles that are too small to see with the naked eye.

What do you think happened to the copper sulfate particles? Where are they now?

The copper sulfate particles have been mixed up with the water particles.

Draw a picture of the particles in the copper sulfate solution in the space. You can use the following symbols to represent each substance:

shaded circles to represent water particles

white hexagons to represent copper sulfate particles

Teacher note: The sketch should show the container with liquid particles at the bottom. In the liquid the black dots should be homogeneously dispersed among the clear ones, in the same way as the sugar particles are dispersed among the water particles in the following diagram:

In the video clip on "How water mixes with a solute to make a solution", the language may be a bit difficult to understand, but if you watch the clip you will get the general idea. However, there is no problem with selling this (and other) clips on the grounds that it uses ideas and language that they (the learners) can access when they get older. You, the teacher, can even challenge the learners to find out about some of the new ideas in this clip and report back to you personally or in class. Forces are also dealt with again in this video - this can be introduced by asking "What keeps the particles of a solid or liquid from moving away from each other?" The answer is that there are forces between the particles.

Soluble substances

soluble substance

insoluble substance

NB: A very common misconception is that sugar or salt "melts" away when added to water. Dissolving (in the case of sugar and salt in water) requires two materials to be mixed together (a solute will dissolve in a solvent), whereas in melting (in the case of ice), there is heating of one material to change its state. A single substance melts when it changes from one state to another. In order to avoid introducing this misconception which then sticks with learners into the later grades, never use the word "melt" when describing dissolving. Emphasise to learners that the sugar does not melt and that melting is different - it is a change of state.

We have a word for substances that form solutions when they are mixed with water. These substances are called soluble substances.

Substances that do NOT form solutions when they are mixed with water are called insoluble substances.

In the next activity we are going to use some findings from a previous activity (Which mixtures are solutions?) to link this new idea to what we know about solutions.

Soluble or insoluble?

INSTRUCTIONS:

The table from the activity Which mixtures are solutions? has been copied below, and an extra column has been added.

Use the extra column to say whether the substance that was mixed with water in the activity is soluble or insoluble.

Table: Soluble and insoluble substances.

Mixture

Is the mixture a solution? (Yes or No)

Is the substance that was mixed with the water soluble or insoluble?

Sugar and water

Yes

Soluble

Salt and water

Yes

Soluble

Sand and water

No

Insoluble

Oil and water

No

Insoluble

Vinegar and water

Yes

Soluble

Copper sulfate and water

Yes

Soluble

QUESTIONS:

Complete the following sentences by writing soluble or insoluble in the open spaces.

Substances that do NOT form solutions when they are mixed with water are called _____ substances.

insoluble

Substances that form solutions when they are mixed with water are called _____ substances.

soluble

In the previous chapter, we saw how to separate mixtures. For example, we could hand sort the objects, sieve the larger grains out of the mixture and decant the oil from the top of the water. But what about a solution? Do you think you can separate the sugar from the solution once it has been dissolved? Let's try to find out the answer to this question!

How can we recover a solute (sugar) from the solution?

Prepare the sugar solution beforehand (or at the beginning of the class so that learners see you mixing) by mixing sugar into water and making sure it is dissolved. You can prepare enough for the whole class to use or do this experiment as a demonstration. Start off by asking learners if they can see the sugar. Revise the concept that it has dissolved into the water to form a solution. Before starting the investigation, ask the learners how they think you could separate or recover the sugar from the solution.

Ask learners if they think you could separate by sieving or filtering. After they answer you, demonstrate filtering by pouring the sugar solution through filter paper placed in a funnel into another beaker. Show the learners the filter paper so that they can then see that there is no sugar left behind on the filter paper. They can fill in their observations in the table.

Ask learners if they think settling will work. You could prepare a sugar solution the day before the class and then leave it overnight in the classroom and tell learners you want to see the next day whether the sugar has settled out of the solution. They can then see for themselves the next day during the next lesson that it has not settled out and that this technique cannot be used to separate a sugar solution. They can fill in their observations in the table.

Continued...

The next step is to see what will happen if we evaporate the water. This probably will not be a logical step for the learners to take. So ask leading questions such as, what do they think will happen to a dish of water if you leave it outside in the sun. Answer: It will evaporate. Note though, that evaporation does not need heat to take place, but the heat from the sun will speed up the process.

Ask learners what they think will happen to the sugar solution if you leave it outside in a dish to evaporate? Will the water evaporate? What will happen to the sugar? The learners should see the need to perform the investigation from asking these questions as the answer might not be obvious.

While you are waiting for the water to evaporate and leave behind the sugar crystals, you can demonstrate another way of recovering the sugar (solute) which is by boiling the sugar solution. Set up a beaker of the sugar solution on a stand over a Bunsen burner. Light the Bunsen burner and allow the solution to boil. Do not put a lot of the sugar solution into the beaker otherwise the demonstration will take too long. Boiling speeds up the process and the last remaining water can be left to evaporate until only sugar crystals are left at the bottom of the beaker. This is called crystallisation.

AIM (What do you want to find out?):

MATERIALS AND APPARATUS:

sugar solution

2 beakers

funnel

filter paper

evaporating dish

stand

Bunsen burner

matches

METHOD:

Pour a small amount of the sugar solution into an evaporating dish.

Place the dish outside, or on a windowsill, in a sunny spot.

Remind learners that evaporation does not require additional heat to take place, but heating speeds up the process.

Leave the dish outside and check regularly to observe what is happening to the sugar solution.

Your teacher will demonstrate whether you can also recover the sugar by boiling the solution.

Record all your observations in the table below.

RESULTS AND OBSERVATIONS:

Method

Result - Could you recover the sugar from the solution?

Sieving or filtering

Settling overnight

Evaporation

Boiling

Which methods worked to recover the sugar from the solution?

Boiling and evaporation.

What was left at the bottom after completing these methods?

Sugar crystals.

Why do you think this happens?

This is because the water evaporates or boils and turns into water vapour. The sugar cannot evaporate and is left behind as a solid in the form of crystals.

Which method do you think works best and why?

Learner dependent answer: They could say boiling as it is faster, or they could say evaporation as it does not require much equipment such as a Bunsen burner, etc.

CONCLUSION:

What can you conclude from this investigation?

Now that we have looked at how to separate a solute from a solution, have you ever wondered just how much sugar you could dissolve in the water? Do you drink tea, for example, and put sugar in? How many teaspoons of sugar do you think you can dissolve in a cup of tea? In the next section we will explore this idea.

Saturated solutions

dissolve

saturated solution

Explanation of new words

Dissolve: When the particles of a solute spread throughout the particles of a solvent, we say the solute dissolves in the solvent to make a solution.

Saturated solution: When so much solute has dissolved that no more of it will dissolve, we say the solution is saturated.

Suppose we were to make a cup of tea and we put in 3 teaspoons of sugar. Mmm... lovely sweet, warm tea!

Now imagine you add three more teaspoons of sugar to the tea. How many teaspoons of sugar did we add?

Six, in total.

When the particles of a solute spread throughout the particles of a solvent, we say the solute dissolves in the solvent to make a solution.

Do you think 6 spoons of sugar will dissolve in the tea? Who has tried this at home? What did you find?

Now let us imagine 3 more teaspoons of sugar is added to the tea. Very sweet tea! Do you think all the sugar will dissolve?

How much sugar do you think we will be able to dissolve in the tea? An infinite amount? A cupful or less? Let's try it out.

How much solute will dissolve?

This investigation makes the ideal demonstration, and could even be given as a homework experiment. It also allows for the extension of learners' understanding of the concept of solubility and saturated solutions. You could heat the saturated sugar solution for the learners to show that more solute will dissolve when the solvent is at a higher temperature (this is mostly true, but not always!). If more sugar is added to the heated solution until it is saturated at the higher temperature, then the solution will be supersaturated when cooled. A sugar crystal can be suspended in the solution before it cools down and more sugar crystals will grow on the crystal and on the thread used to suspend the crystal. The less the solution is disturbed, the larger the crystals will grow.

MATERIALS:

clear container (a glass beaker would be best, although a large yoghurt tub would also work, but not if you decide to heat it later)

tap water

small packet of sugar

plastic spoon for scooping and stirring

INSTRUCTIONS:

Measure half a cup of water into the container.

Add a teaspoon of sugar to the water. Stir until all the sugar has dissolved.

Add another teaspoon and stir again.

Keep adding teaspoons of sugar until no more sugar can dissolve.

QUESTIONS:

How many spoons did you add until no more sugar dissolved?

How did you know that no more sugar could dissolve?

The sugar stopped dissolving and sank to the bottom of the container.

Complete the following sentences by writing saturated or unsaturated in the open spaces.

When no more solute can dissolve in a solution, we say it is a _____ solution.

When more solute can be dissolved in a solution, we say the solution is _____.

saturated

unsaturated

Growing sugar crystals (video) http://www.youtube.com/watch?v=P4n9jJXHCKE

Now let's have some fun with saturated solutions!

Making sugar crystals

Sugar crystals can take a few days to a week to "grow", so set up this experiment and then leave the jars on the windowsill where they will not be disturbed. You can use different coloured food colouring so that learners have brightly coloured crystals at the end. Each learner can make their own or you can scale up the quantities below and make it in one big beaker, or possibly three different ones with different colours. The quantities listed below are for one crystal to grow in one jar. However, it would be ideal for each learner to have their own crystal.

MATERIALS:

1/2 cup water

1 cup table sugar

clean glass jar

food colouring

pencil

rough string (cooking twine works great)

beaker or pan for boiling water and making solution

spoon

stove or Bunsen burner and stand

INSTRUCTIONS:

Tie a length of string onto a pencil. The string should be long enough to reach almost to the bottom of your glass jar.

Make a saturated sugar solution by boiling the water in the pan, slowly adding sugar a teaspoon at a time. If you have a Bunsen burner and stand, you can do this in a beaker over the flame.

Stir after each spoonful and keep adding sugar until the sugar won't dissolve any more in the water. If you do not add enough sugar, your crystals will not grow quickly. If you use too much sugar, your crystals will grow on the undissolved crystals and not on the string.

Pour some food colouring into your saturated solution to give the crystals a colour.

Pour your solution into the clear glass jar. If you have undissolved sugar at the bottom of your container, avoid getting it in the jar.

Place your sting inside the glass jar.

A tip is to weight the string with something heavy so that it does not touch the sides of the glass jar.

Place your jar where it will not be disturbed and check on your string each day and observe the crystal growth.

Allow the crystals to grow until they have reached a size that you desire, or until they have stopped growing. You can pull the string out and allow the crystals to dry. You can eat them or keep them!

The best crystals form when the process happens slowly and the water cools down slowly. The cooled solution has a concentration above the saturation point and is said to be supersaturated. Crystal will more easily form when they have a place to start growing, like on the string.

QUESTIONS:

Copper sulfate crystal time lapse (video) http://www.youtube.com/watch?v=caGX6PoVneU&feature=related

How long did it take for crystals to start forming on the string?

Learner dependent answer.

What are the crystals made of?

Sugar

Why do you think we boiled the water when dissolving the sugar in the solution?

This might be quite difficult for learners to answer but have this question as a class discussion. Boiling the water allows one to dissolve more solute than if the water was cool or at room temperature. This results in a supersatured solution.

An example of crystals in nature

insoluble substance

Have you ever visited a cave? Inside, you may have seen crystal formations called stalactites and stalagmites. Stalactites and stalagmites form inside limestone caves. Stalactites hang down like icicles and stalagmites grow from the floor of the cave upwards. Stalactites and stalagmites always occur in pairs. Caves form when water slowly dissolves the limestone underground. The dissolved limestone can crystallise again when the water evaporates. This is also a slow process and it happens when water drips down from the ceiling of the cave over a long period of time. The water drops that land on the floor of the cave evaporate over time, and where they fall on the same spot repeatedly, a stalagmite eventually forms. Over many thousands of years, the stalactite and stalagmite may connect to become a column.

Stalactites and stalagmites forming in a cave.

Cango Caves in Oudtshoorn in South Africa

Insoluble substances

We have a word for substances that do NOT form solutions when they are mixed with water. These substances are called insoluble substances.

Can you remember what substances are called that DO form solutions when they are mixed with water? Write the term below.

Soluble substances

Some substances that are insoluble in water may be soluble in other solvents! Think about this for a moment: Is nail polish soluble in water? No, of course not, or it would be possible to wash it off! What would be a good solvent for nail polish?

Nail polish remover will be a good solvent.

What have we learnt about solutions as special mixtures?

Soluble substances dissolve in water and insoluble substances do not dissolve in water.

Water is not the only solvent. Some substances which are not soluble in water are soluble in other solvents. When no more solute can dissolve in a solution, we say it is a saturated solution. An unsaturated solution is one where it is possible to dissolve more solute in the solvent.

Solutions are special kinds of mixtures. When we want to decide whether a mixture is also a solution, we can use the following questions to decide:

Question about the mixture

The mixture is a solution

The mixture is NOT a solution

Can you see the solute in the solvent?

No

Yes

Does the solute settle out?

No

Yes

Can the mixture be separated using filtration?

No

Yes

Can the mixture be separated by evaporation?

Yes

No

A solution is a special kind of mixture. Like all mixtures it consists of two (or more) substances mixed together.

A solution is made up of a solvent (such as water) in which one or more solutes have been dissolved.

In a solution, the solute looks as if it disappears into the solvent. This is because the particles of the solute and the solvent become closely mixed.

There are many kinds of solutions, but the most well-known ones are mixtures of a solid and a liquid, such as sugar and water.

Not all substances dissolve in water. Those that dissolve are called soluble substances; those that do not dissolve are called insoluble substances.

Solutions cannot be separated by sieving, filtering, hand sorting, or settling and decanting. This is because solute particles are dispersed between the solvent particles.

Solutions can be separated by heating so that the solvent evaporates. The dry solute will be left behind.

When we have dissolved so much solute in the solvent that no more solute can possibly dissolve, we say that the solution is saturated.

In the activity Soluble or insoluble? we explored some substances, and found that sand is insoluble in water.

In the same activity we found that sugar is soluble in water.

Can you remember how to separate sand and water? (Hint: Look at the activity Mixing a solid and a liquid.) Write it down below.

In the activity 'Mixing a solid and a liquid' we saw that a mixture of sand and water can be separated by passing the mixture through a towel.

In the picture below a mixture of sand and water is poured through a filter. What is this process called?

Filtering/filtration

Why do the sand grains stay behind on the filter paper, but the water passes through it?

The sand grains are too large to pass through the paper. The water particles are very small and can easily pass through the filter paper.

What was the mixture of sugar and water called? (Hint: It was a special kind of mixture called a.. ?)

Solution

What would happen if the mixture of sugar and water is poured through a filter? Would it be possible to separate the water and the sugar?

The sugar and water would pass through the filter and it would not be possible to separate them in this way.

What happens to the sugar when it dissolves in the water?

The sugar crystals separate into individual particles that mix with the particles of the water.

Why is it not possible to separate a solution through a filter?

Because the particles of the solute and the solvent are thoroughly mixed and are of roughly the same size.

Describe how you can get the solid sugar back from the sugar solution.

Learners must describe the process of evaporation or boiling which leaves behind the sugar crystals.

Draw a flow diagram to show how a mixture of salt and sand can be separated. Each step must be clear. Your first step will be to mix the salt and sand with water.

These two substances cannot be separated by sieving as they will mostly have the same grain size. The first step is to mix the the salt and sand with water so that the salt dissolves. You then filter the mixture so that the salt solution passes through the filter paper whereas the sand remains behind. Then to regain the salt crystals, you evaporate or boil off the water to be left with the salt crystals at the end.

Dissolving

What does rate of dissolving mean?

How does temperature affect the rate of dissolving of a substance?

How does stirring affect the rate of dissolving of a substance?

How does the size of the solute grains affect the rate of dissolving of a substance?

What is dissolving?

In this section we are going to make more solutions. We will perform some experiments to see if we can make our solutes dissolve faster. Before we do that, we have to answer an important question: is melting and dissolving the same? What do you think?

The difference between melting and dissolving is very relevant, and mistaking dissolving for melting is a pervasive misconception at this stage of the learners' development.

Is melting and dissolving the same?

In this activity we are going to explore the differences between melting and dissolving. We have learnt that matter can exist as 3 different states: solid, liquid and gas.

INSTRUCTIONS (Part 1)

Watch the following short video clip to remind yourself how a solid, liquid and gas are different from each other. You should look out for the part where the states change. The solid changes to a liquid and then the liquid changes into a gas. Remember that a state change is when a substance changes from one state (i.e. solid) to another state (i.e. liquid).

http://www.youtube.com/watch?v=-CwnAxylyFo&feature=related

The following picture shows how the different states of matter are related to each other. It also shows what the different state changes are called.

QUESTIONS:

What is needed to change a solid into a liquid?

Energy or heat

What is the process called when a solid changes into a liquid?

Melting

Fill in the missing words:

The particles in a _____ have fixed positions. When the solid melts, the particles are free to move from their positions. The state in which particles are close to each other but free to move around is called the _____ state.

Answers: solid, liquid

INSTRUCTIONS (Part 2)

Do you remember dissolving sugar in water in the previous chapter?

The following picture shows what we would see if we could shrink ourselves down to the size of water and sugar particles (molecules).

A solution of water and sugar molecules (particles)

Look carefully at the picture and then answer the following questions.

QUESTIONS:

Why is the sugar no longer visible? Give a reason.

The sugar does not disappear. It is not visible anymore as the sugar crystals have broken up into the individual sugar molecules, which we cannot see with the naked eye.

How can we be sure the sugar has not "disappeared" and that it is still there?

We can get the sugar back in crystal form by evaporating all the water away.

How is the picture of the sugar and water mixture different from the picture of the liquid which is shown below?

The picture of the sugar and water has two kinds of particles. The picture of the liquid only has one kind of particle.

The particles in liquid water.

What do we call it when we have two or more substances combined?

A mixture.

Can we say that the sugar melts? Give a reason.

No, the sugar does not melt. The sugar particles are free, but they are mixed with the water.

Rates of dissolving

Explanation of new words:

Temperature: tells us how hot or cold an object is. We measure temperature with a thermometer.

Grain size: the size of the particles of the substance. A big lump has a large grain size while powder has a small grain size.

Variable: something (an aspect of the investigation) that we change during an experiment. For instance, in an experiment to compare how fast a solute dissolves at different temperatures, we would change the temperature of the solvent. This means temperature is a variable in this experiment.

This section offers a great opportunity for learners to experience aspects of scientific experimentation that are a little more advanced than what they have done thus far. You could talk about controlling variables (changing just one variable in a set, and keeping all the others constant), and how to identify the independent and dependent variables. They will also be introduced to coming to a conclusion at the end of an investigation. Finally, they are introduced to the kinetic molecular model of matter when they learn that particles move faster when they are given energy (just like children!) and when they are moving faster they collide more, which speeds up dissolving. All of this provides a solid foundation for building a more complex understanding of these concepts in later years.

The rate of dissolving refers to how quickly a solute dissolves in a solvent. The word "rate" has many meanings. In science, when we use the word "rate" we usually mean how fast or how slow.

Tom likes his coffee sweet, with 3 teaspoons of sugar. For the coffee to taste sweet, the sugar must be dissolved. Here is a picture of a cup of coffee. Answer the questions that follow.

temperature

grain size

variable

rate

A cup of coffee http://www.flickr.com/photos/preppybyday/6703560771/

Is the cup of coffee a mixture? Give a reason.

Yes, because it is a combination of different substances.

Is the cup of coffee a solution? Give a reason.

No, it is not a solution as a whole. The milk is suspension, as it is cloudy, and does not dissolve in the water. The coffee granules are an infusion in the water. However, the sugar does dissolve in the water and this forms a solution.

Teacher note: This might be hard for learners to answer, but it is important to note here that "cloudiness" implies that tiny aggregates or globules are suspended in the liquid or gas base. Transparency implies the particles of the substances are separated from each other and dissolved. So the milk is a suspension and not a solution in the water.

Make a list of the components in the coffee mixture.

Coffee, sugar and milk in water

Which component is the solvent?

Water

Is the sugar a solute or a solvent?

Solute

What could Tom do to make sure that the sugar dissolves quickly?

Tom could stir the coffee, Tom could use finer sugar, or Tom could stir in the sugar before the milk is added (assuming the milk is not heated).

Stirring a solution is just one of the things we can do to make a solute dissolve faster.

We are going to perform 3 investigations to explore the factors that affect the rate of dissolving of sugar (a solute) in water (a solvent).

In the first investigation, we will explore whether salt dissolves faster in hot or cold water. What do you expect?

Does salt dissolve faster in hot or cold water?

AIM:

To investigate how temperature affects the rate of dissolving

MATERIALS AND APPARATUS:

3 clear containers (glass beakers are ideal, but small yoghurt tubs will also be suitable)

table salt

very hot water (not boiling)

tap water (at room temperature)

ice water

teaspoon

stopwatch or clock with second hand

Try to use sea salt (or any brand without "free flowing agent" - This is usually cornflour and obscures observations by forming a cloudy suspension). Alternatively, one can just use sugar here.

METHOD:

Measure the same quantity (100 ml) of tap water, hot water and ice water respectively into the three containers. Look at the diagram of the setup.

Place one teaspoon (5 ml) of salt into the container with the hot water.

Stir the solution by moving the teaspoon once back and forth through the water.

Stirring must occur at the same, regular rate for comparisons to be drawn. Let each group agree on a way to ensure this (perhaps by counting each full "stir" of the spoon).

Measure the time it takes for the salt to dissolve completely. Record the time in the table below.

Repeat steps 3-5 with the tap water and record the time it takes for the salt to dissolve in the table.

Repeat steps 3-5 with the ice water, and record the time it takes for the salt to dissolve in the table.

This step should be done with the ice OUTSIDE the water used for mixing. Either very cold water from a fridge can be used, or the mixing container should be placed on a bed of crushed ice. The presence of the ice in the mixing water obviously has nothing to do with the rate of dissolution. Additionally, some of the salt may end up on top of the ice and freeze there, creating a situation where it may appear that the salt dissolved quicker in the cold water than the room temperature water.

RESULTS:

The effect of temperature on dissolving

Situation

Time to dissolve (in seconds)

Salt in hot water

Salt in tap water

Salt in ice water

QUESTIONS:

What did we compare in this investigation?

We compared how fast salt dissolved in hot water, water at room temperature, and ice water.

Name three things that were the same about the three situations.

The amount of water we used

The amount of salt we added to the water

The amount of stirring

What did we change in this investigation?

The temperature of the water.

Teacher note: This is an opportunity to introduce the term variable (see New Words above). The variable that we change (manipulate) is called the independent variable.

We measured the temperature of the water. What else did we measure?

We measured the time it took for the salt to dissolve.

Teacher note: The variable that we measure is called the dependent variable. In this case time is the dependent variable.

In which situation did the salt dissolve the fastest?

The salt dissolved fastest in the hot water

CONCLUSION:

The salt crystals dissolved _____ in the hot water than the cold water. Temperature affects the rate of dissolving. When we increase the temperature of the solvent, the rate at which the solute dissolves _____.

Answer: faster, increases.

Extension question: Why do you think the salt dissolves faster in the hot water?

Teacher note: This is an opportunity to bring the energy concept into the conversation. Children move faster when they have more energy! Particles also move faster when they have more energy. When a solute dissolves in a solvent, the solute particles spread out among the solvent particles. This process happens much faster when all the particles are moving faster.

In the second investigation we will explore whether coarse salt dissolves faster than fine salt. What do you expect?

Does fine salt dissolve faster than rock salt?

To investigate how grain size affects the rate of dissolving

MATERIALS AND APPARATUS:

2 clear containers (glass beakers are ideal, but small yoghurt tubs will also be suitable)

fine table salt

coarse rock salt

teaspoon

tap water

stopwatch

METHOD:

Measure the same quantity (100 ml) of tap water into each container.

Place one teaspoon (5 ml) of fine table salt into the first container.

Stir the solution and measure the time it takes for the salt to dissolve completely. Record the time in the table below.

Repeat steps 2-3 with the coarse rock salt.

RESULTS:

The effect of grain size on dissolving

Situation

Time to dissolve (in seconds)

Fine salt in water

Coarse salt in water

QUESTIONS:

What did we compare in this investigation?

We compared which dissolved faster in water, fine salt or coarse salt.

Name three things that were the same about the three situations.

The amount of water we used

The temperature of the water

The amount of stirring

What did we change in this investigation?

The grain size of the salt

Teacher note: Here, you should explain the term 'grain size' by pointing out the differences in the sizes of the salt crystals. You should also try to convey that the same quantity (mass) of table salt would contain more grains if the grains were smaller.

Another opportunity to introduce the term variable (see New Words above). The variable that we change (manipulate) is called the independent variable.

What did we measure?

We measured the time it took for each type of salt to dissolve.

Teacher note: The variable that we measure is called the dependent variable. In this case the dependent variable is time, and the independent variable is grain size.

Which type of salt dissolved faster?

The fine salt dissolved faster.

Complete the conclusion below by filling in the missing word or words.

CONCLUSION:

The fine salt dissolved _____ than the coarse salt. Grain size affects the rate of dissolving. When we increase the grain size of the solute, the rate at which the solute dissolves _____.

Answer: faster, decreases.

Extension question: Why do you think the fine salt dissolves faster than the coarse salt?

Teacher note: This is an opportunity to bring the concept of surface area into the conversation.

Ask the learners to say which would contain more grains, a teaspoon of fine salt or a teaspoon of coarse salt.

Sketch the following two scenarios:

In the first scenario there are 30 stones and 30 children. Each child should pick up one stone, and carry it away. Only once the child has moved out of the way can the next child in line pick up a stone. If all the stones are in one large pile it will take a long time for all the stones to be picked up and carried away. This scenario can be compared to the larger grain size particles dissolving in the water.

In the second scenario there are also 30 stones and 30 children, but this time the stones are in 10 small piles of 3 stones each. In this scenario it is possible to carry 10 stones away at a time, because there are many more small piles. This scenario can be compared to the smaller grains size particles dissolving in the water.

This is roughly similar to the effect of smaller grain size, the more grains we have, the faster the solute particles can be 'carried away' by the solvent particles.

In the third investigation we will explore whether salt dissolves faster in water when it is stirred. What do you expect?

Does stirring increase the rate of dissolving?

In this investigation, the learners must come up with their own method (experimental design) to test whether stirring has an effect. You must provide the equipment. They can then look at the diagram of the setup and note what materials and apparatus they will need. After completing the investigation, they must also write out a method themselves. Learners can work in groups to do this.

In this investigation, you are going to design your own experiment to answer the question. Use your knowledge of the previous two investigations to help you. Look at the materials and apparatus that have been provided, as well as the diagram, to design your investigation and then write it out in the spaces below.

To investigate how stirring affects the rate of dissolving

MATERIALS AND APPARATUS:

Make a list of what you will need to complete this investigation:

2 clear containers (glass beakers are ideal, but small yoghurt tubs will also be suitable)

fine table salt

tap water

teaspoon

METHOD:

Write out the steps that you will follow to complete the investigation. Remember to include measurements.

Place a teaspoon of salt in each container.

Add the same amount of water (half a cup) to each container.

Stir the mixture in the first beaker but not the mixture in the second beaker.

Record your observations in the table.

RESULTS:

The effect of stirring on dissolving

Situation

Time to dissolve (in seconds)

Salt in water (with stirring)

Salt in water (without stirring)

QUESTIONS:

What did we compare in this investigation?

We compared which dissolved faster in water, a salt solution that is stirred or a salt solution that is not stirred.

Name 3 things that were the same about the 3 situations.

The amount of water we used

The temperature of the water

The amount of salt we used

What did we change in this investigation?

We investigated whether or not the mixture was stirred.

What made the salt dissolve faster: stirring, or not stirring?

The salt in the stirred solution dissolved faster.

CONCLUSION:

The mixture that was stirred dissolved _____ than the mixture that was not stirred. Stirring affects the rate of dissolving.

Answer: faster

Extension question: Why do you think stirring makes the salt dissolve faster?

Particles move faster when they are stirred. When a solute dissolves in a solvent, the solute particles spread out among the solvent particles. This process happens much faster when all the particles are moving faster.

The time it takes for a substance to dissolve is called the dissolving rate or the rate of dissolution.

The rate at which a substance dissolves can be affected by 3 factors, namely:

the temperature of the solution;

whether or not the solution is stirred (or shaken); and

the grain size of the solute.

A solute will generally dissolve faster if the solvent in which it dissolves is warm.

A solute will dissolve faster when the solution is stirred or shaken.

A solute will dissolve faster if the size of its grains is small.

What are the three factors that affect solubility? Write a sentence describing how they affect solubility.

The three factors that affect solubility are temperature, grain size and stirring. Increasing the temperature increases solubility, decreasing the grain size increases solubility and stirring increases solubility.

Write 3 examples where we use the factors that affect dissolving in our daily lives.

Any appropriate examples will do, for instance:

stirring tea or coffee to make the sugar dissolve

heating water to make salt dissolve when cooking; and

using fine salt as opposed to coarse grains when dissolving in water to make a salt solution for cooking or rinsing, etc.

Complete the following crossword puzzle:

Use the words in the box below, and the clues that are given underneath.

soluble solute solvent dissolves stir decrease solution saturated

DOWN:

When a solute can dissolve in a solvent we say it is … (7 letters)

When we lower the temperature of the solvent, the rate of dissolving of the solute will … (8 letters)

The substance that dissolves in the solvent is called the … (6 letters)

The mixture of solute and solvent is called the … (8 letters)

When we cannot dissolve any more solute in a solution, we say the solution is … (9 letters)

ACROSS:

The substance that dissolves the solute is called the … (7 letters)

The solute … in the solvent. (9 letters)

When we want the solute to dissolve more quickly we should … the solution. (4 letters)

Mixtures and water resources

Why is it important for humans, plants and animals to have access to clean water?

What is the difference between clean water and polluted water?

What are the different things that pollute water?

Why should wetlands be protected?

We have learnt that water can dissolve many substances - water is a good solvent. When water has unhealthy substances in it, we say the water is polluted. Polluted water is not clean.

Water pollution

When is water clean? We could say that clean water is free of pollutants.

pollution

effluent

sewage

What are pollutants? Pollutants are substances (or objects) that do not naturally belong in the water and are harmful to us and to the environment.

Pollutants may be any of the following:

Insoluble pollutants: these are things that do not dissolve in the water but make it dirty, such as oil, garbage and toilet waste (sewage).

Soluble pollutants: these are chemicals (eg. soaps, fertilisers) and poisons (eg. insecticides).

Living germs (bacteria) that can cause people or animals to get sick.

Water pollution (video)http://www.youtube.com/watch?v=QqNUTlY5foQ

There is an interesting term in the video clip on Water Pollution: "natural pollutants". It is a nice topic for a short discussion. Even things that are quite natural can act as pollutants when released in large quantities. Human sewage is an extreme example. Most ecosystems are "buffered" against abnormal amounts of such substances, but only up to a certain point.

In the next activity we will discuss pollution and where it comes from.

Thinking about pollution

INSTRUCTIONS:

We are going to discuss pollution.

The following pictures of different polluted water sources, and the questions that follow, are meant to guide the discussion.

Pollution in a pond

A polluted river

Pollution on the coast

People have been using this stream to dump rubbish.

An oil spill

QUESTIONS:

Look at the pictures above and make a list of all the objects that do not belong in the water.

Plastic bags, tyres, paper, polystyrene, bottles, shopping trolley, tins, metal rubbish bin, oil

What are the three main categories of pollutants found in water?

Insoluble pollutants

Soluble pollutants

Disease-causing bacteria (germs)

Which category of pollutants would you be able to see with the naked eye?

Insoluble pollutants

Which categories of pollutants would you not be able to see with the naked eye?

Soluble pollutants and germs

How do you think insoluble pollutants end up in water?

People allow garbage to fall into the water instead of placing it in a garbage bag for collection, and may even use the water as a toilet releasing germs into the water.

How do you think soluble pollutants end up in water?

There are many examples:

Rainwater can wash fertilisers and pesticides from farm lands into the rivers and other water sources.

People can allow their household water (that contain soap and detergents) to run directly into the rivers.

Industries can release polluted effluent into the rivers. (Effluent is the term for liquid waste or sewage discharged into a river or the sea.)

How do you think bacteria that cause illness like diarrhoea and cholera end up in water?

Bacteria get into the water mainly through people and animals using the water sources as a toilet. People and animals have bacteria that occur naturally in the digestive tract, but outside of this environment, they can be harmful.

How do you think oil ends up in the water, especially in oceans?

Cars drop oil and other chemical pollutants everywhere. These wash into the rainwater collection system and straight into rivers and seas. More dramatic disasters also pollute the ocean with oil. Oil may spill from a faulty oil rig in the ocean, or from a ship carrying oil which can leak or burst open.

What do all 3 categories of pollutants have in common?

Learners may say: 'They do not belong in clean water'. Help them to see that it is mainly through human activity that water sources become polluted.

BP oil spill in Gulf of Mexico (video) http://www.youtube.com/watch?v=-OVNd6Fa9fg

Have you noticed that humans and their activities are often the reason why water becomes polluted?

As humans, we often forget that we are sharing this natural resource with many other organisms. Many of our activities can change the quality of the water in a way that affects the health and behaviour of other organisms.

Importance of wetlands

wetland

water table

waterlogged

Nature has special methods of cleaning polluted water. In nature, water is purified in natural environments called wetlands. Wetlands are very efficient natural 'water treatment' facilities, and in this section we will learn how they work.

What are wetlands?

Some useful documents are available at these links and are free to use as long as you acknowledge them as the source. A suggestion is to get your school to print them in colour.

http://www.wetland.org.za/ckfinder/userfiles/files/2_1-%20MWP%20wetland%20basics%20presentation%201%281%29.pdf and http://www.wetland.org.za/ckfinder/userfiles/files/2_2-%20MWP%20wetland%20basics%20presentation%202.pdf

An area is a wetland if it has the following:

waterlogged soil,

water-loving plants and

a high water table.

If soil is waterlogged, it means that it is full of water. The water table refers to the level in the ground where all the soil below this level is waterlogged (full of water). If an area has a high water table, then this level is close to the surface. This means water will not filter down into the ground but remain on the surface forming a wetland.

Wetlands in South Africa http://wetland.org.za/

Examples of wetlands are:

marshes

floodplains

swamps

lakes and pans

seeps and springs

estuaries

river banks

Look at the pictures of different wetlands.

Isimangaliso Wetland Park (website) http://www.isimangaliso.com/

Wetlands are not necessarily wet throughout the year.

A temporary wetland is wet between 1 and 4 months of the year.

A seasonal wetland is wet during the rainy season. This means it will be wet between 5 and 11 months of the year, depending on the length of the rainy season.

A permanent wetland is wet throughout the year.

In South Africa, the most well-known wetlands are the St. Lucia wetlands in KwaZulu-Natal.

Why are wetlands so important?

Wetlands are very special places that should be protected. Why are they so important?

Three unique abilities of wetlands make them very important.

Wetlands are like giant sponges:

Wetlands soak up water and store it. During a drought, when there is not much rain, this stored water can help to keep rivers and streams flowing so that animals and plants can stay alive.

Wetlands slow down flood waters:

Water that is 'in flood' flows so strongly and quickly that it becomes dangerous. It can drown people and animals and it can cause damage to property and also to the environment, through soil erosion. Floodwater slows down when it flows into a wetland, because the wetland is a large area that can hold a large amount of water.

Wetlands are natural filtration systems for purifying water:

As water flows through the wetland, it is filtered. Plants in the wetland trap soil particles and sediments, nutrients, as well as pollutants and disease-causing organisms which make the water unsafe.

With regards to the pollutants being filtered from wetlands, it is only certain kinds, and only in certain loads. Insoluble wastes such as plastics should not end up in a wetland. Bacteria and other germs are neutralized. Chemical pollutants such as heavy metals are trapped, but if they become concentrated in too large amounts, they need to be taken out by removing plant matter that has absorbed them.

Making a model of a wetland

Teacher note: The reason for doing this activity is to help learners understand how different surfaces, especially those covered in plants, allow water to drain at different rates allowing soil to retain much of the water, and other surfaces to lose a lot of water. This will also show how wetlands help to slow down water and filter it.

MATERIALS:

grass moss or other garden moss

bricks

sand

soil

shallow plastic trays (about 7-10 cm deep)

hardboard

watering can

measuring tool to measure 2 litres of water

hand or electric drill (to be used only under STRICT ADULT SUPERVISION)

watch or stopwatch

plastic window box

The watering can must be the kind with a 'shower-type head' at the front that will simulate rain falling

INSTRUCTIONS:

Drill a hole in the middle and at the bottom of one side of the plastic box.

Pack 2 layers of bricks, the window box, and the hardboard as shown in the illustration.

Position the hole you drilled in the tray over the centre of the hardboard so you do not accidentally lose water over the sides that should run into the window box.

Fill your watering can with 2 litres of water.

Setup for the drainage experiment

Moss is found in many wetland areas like marshes, bogs and waterways. Place the moss inside the tray over moist soil. Pour the 2 litres of water slowly and evenly over the moss. Time how long it takes for the water to filter through the moss and run into the window box.

How long did it take the water to run into the window box?

Why do you think it took the water this long to drain off?

Moss holds water very well and that is why it took so long for the water to drain off.

Perhaps someone should remain timing that experiment while the rest move on to the others.

Repeat this experiment with sand - this is what happens to rainwater in the Namib or Sahara Deserts.

How long did it take the water to run into the window box?

Why do you think it took the water this long to drain off?

Sand does not hold water very well at all. That is why the water drained off so quickly.

QUESTION:

What did you learn from doing this experiment about the relationship between plants and water drainage in a wetland?

Learner-dependent answer.

Wetlands are also important as they provide a habitat to many different plant and animal species. Wetlands are important because of their biodiversity.

Ask the learners why biodiversity is important. This is a link back to what they did in Life and Living.

Do you remember studying habitats in Gr. 4 and Gr. 5? What does a habitat provide to an organism?

A habitat provides food, water, shelter, a place to raise young, a place to hide from predators.

Discuss with your partner what you understand by the term 'biodiversity' and write it down below

Biodiversity refers to the variety of organisms (plants and animals) in a specific area. An area with a high biodiversity will have many different species of plants and animals.

Let's now do some research about the wetlands in South Africa and their importance.

Before doing the following activity, it is recommended that you show this Powerpoint presentation to the learners:

http://www.wetland.org.za/ckfinder/userfiles/files/2_1-%20MWP%20wetland%20basics%20presentation%201(1).pdf

If this is not possible, the presentation could be given to the learners in printed format.

Researching the different wetlands in South Africa

MATERIALS:

pamphlets, posters and any other reading material on wetlands

books or other reading material from home, or printed pages from the internet

poster material: cardboard, glue, colour pencils, scissors, pictures, etc

Arrange a visit to a nature reserve to study a wetland area firsthand. Or invite a speaker from a nature conservation site (such as SANParks) to talk to your class about wetlands. BEFORE the visit: tell learners to read through the information brought to school and some of the books and reading material in your class. From this information, set at least 5 questions that you could ask the Nature Conservation Officer when s/he comes to visit your class, or when you go on the outing to the nature reserve. At least 2 of these questions should focus on the dangers to wetlands.DURING the visit: Tell learners to REMEMBER to take many notes while listening to the Nature Conservation Officer.AFTER the visit: In their groups, learners must make a poster about wetlands, using the questions to guide them. NB. If you do not manage to visit a wetland, learners must still complete the research task by reading up on the internet and in books to answer the questions and present a poster.

INSTRUCTIONS:

You might get to visit a wetland near your school or hear a talk by a conservationist.

If you do not get this opportunity, you must still complete the project by doing research in books, pamphlets and on the internet and answer the questions below.

Present your report as a poster.

QUESTIONS TO ANSWER IN YOUR REPORT:

What is a wetland?

What does a wetland do for the environment?

What does a wetland do for plants and animals?

What does a wetland provide for humans?

What are the environmental dangers that wetlands face?

Choose a specific wetland and assess the habitats, biodiversity and water quality of this wetland.

What would the impact be to biodiversity and water quality if this wetland was lost?

Wetlands should be protected because:

they are natural water-purification systems;

they act like sponges to store water in the wet season and supply water in the dry season; and

they slow down flood water to prevent damage to property and the environment.

Clean water is vitally important to ensure the health of humans, animals and plants.

Water can be polluted by insoluble substances, soluble substances and disease-causing germs.

Wetlands act as natural water purifiers because they can absorb soluble and insoluble impurities from water and they regulate water flow across the landscape.

Look at the picture below of the bird covered in oil and answer the questions.

A bird covered in oil. http://www.flickr.com/photos/19378856@N04/2037098785/

How do you think the oil got into the water that this bird lives in?

An oil spill from a ship or oil rig

Is oil a soluble or insoluble water pollutant?

Oil is insoluble as it floats on top of the water.

How will the oil damage this bird and other sea animals?

The oil coats their feathers or skin making it hard for them to fly. It is very sticky and very difficult to remove. The oil can get into their lungs and stomachs which will kill them. Oil also kills fish (possibly the bird's food source) because it prevents oxygen from the air dissolving in the water (oxygen is insoluble in oil).

List some of the dangers that wetlands face.

Learners could list any of the following:

drainage of wetlands for pastures and crops

overgrazing that leads to soil erosion

incorrect burning that leads to soil erosion

timber production

incorrect siting of dams

pollution

mining activities in wetlands

urban development

All the above human activities can affect the water flow and water quality of the wetland and this can ultimately destroy the wetland.

Search the wordsearch puzzle for the types of animals found in wetlands.

See if you can find:

clam

crayfish

mosquito

heron

frog

egret

dragonfly

turtle

fish

shrimp

crab

salamander

duck

Processes to purify water

Why is a clean water supply so important?

How can water be cleaned?

How is water cleaned by municipalities to ensure that we have clean water in our homes?

Clean water

purify / purification

sewage: waste matter carried away in sewers or drains

raw water

still

Have you ever seen a sign like the one in the picture? This sign is a warning that the water is not clean and humans should not drink it as it could be dangerous to your health. If it is unsafe for consumption, it is also unsafe for swimming.

A warning against drinking polluted water

What does 'clean water' mean to you?

Clean water is water that is free of pollutants.

Can you remember what pollutants are? Write it down below.

Pollutants are things that do not belong in the water. Insoluble substances (oil, rubbish and waste), soluble substances (chemicals and poisons) and germs are all pollutants.

We have also learned that nature has special methods of cleaning polluted water. Water purification happens in special natural environments called wetlands. Wetlands are very efficient natural 'water treatment' facilities, but they work slowly. Humans, animals and plants need fresh water every day, and for this reason we have to clean our dirty water so that it can be reused. Cleaning dirty water is what this section is all about.

Why do we need clean water?

Why is it so important for humans, plants and animals to have clean water?

Our bodies are contain a lot of water. In fact you are mostly water! We need water every day because we lose water everyday with the waste our bodies produce. The water we drink must be clean to prevent us from becoming sick or being poisoned.

Plants and animals need clean water too, so that they can grow and be healthy. We need healthy plants and animals in our environment because they provide an ecological balance and food.

Water is also used for fun. Water sports are a very popular recreational activity and include things like swimming, surfing and waterskiing. We want clean water in our seas and lakes so we can enjoy being in the water without becoming ill.

Water is needed for humans to avoid dehydration; the amount you need each day depends on the temperature, how much activity you are involved in and other factors.

How can water be cleaned?

Imagine you are in a place without clean water. The only water around is a muddy stream. How can the dirty water be made clean enough to drink? When thinking about how to purify water, we need to consider what it is that we need to do to separate the contaminating particles from the water. The muddy water is actually a mixture of sand and water, and possibly other contaminants.

Do you remember in the beginning of the term we looked at different ways to separate out mixtures? What are some of these ways?

Filtering/filtration, hand sorting, sieving, evaporation, distilling/distillation, decanting, boiling

Which methods do you think would be useful to separate the large impurities from the dirty water?

Filtering, sieving (possibly hand sorting)

Which methods would be useful to remove the soluble impurities from the dirty water?

Evaporation, boiling, distilling

Let's investigate some different ways to clean water at home or at school.

Water purification tablets can be used in emergencies such as a flood or earthquake when you do not have access to clean water. The tablets remove microscopic impurities and chemicals that could harm you.

Cleaning water in a still

MATERIALS:

clean, dry small pot/container

muddy water

big, deep cooking pot

ruler

1 marble or clean stone

plastic cling wrap

INSTRUCTION S:

Pour the muddy water into the big pot until it is about 5 cm deep (you can use the ruler to measure the depth of the water).

Place the smaller pot/container inside the bigger pot.

The rim of the smaller pot/container must be lower than the rim of the bigger pot so that the water which condenses on the cling wrap has space to run down to the centre where the stone/marble is weighing it down and drip into the smaller pot/container.

Cover the bigger pot with plastic cling wrap.

Place a marble or stone in the middle of the plastic wrap so that it is above the small pot/container inside the pot. You have now made a still for purifying water.

Leave the still out in the sun for a day.

You should continue with the activity after the still has been out in the sun for some time.

Look carefully at the still and answer the questions below.

If you have a phone with a camera, you could take pictures of the still and show them to your class.

QUESTIONS:

What do you notice about the inside of the smaller container? Is it wet or dry?

The small container is wet on the inside.

What do you notice about the cling wrap? Is it wet or dry?

The cling wrap is wet.

Write a paragraph to explain how the water got inside the yoghurt tub. You can use words from the following list, but you can also add your own words:

energy, sun, evaporate, water, water vapour, condense, drip, clean

Learners may write:

Energy from the sun caused the water in the pot to evaporate. Since the pot was sealed with cling wrap, the water vapour condensed against the cling wrap. The marble made the cling wrap dip in the middle. The condensed water slid down and dripped into the smaller container. The water inside the cup was clean.

Why is there no dirt inside the small container/pot?

Dirt does not evaporate.

Where was the dirt at the end of the experiment?

The dirt stayed in the big pot.

Make a poster of the process. You can draw pictures or use the photos you took of the experiment.

Can you remember what method we used to remove sand from water in the activity: Mixing a solid and a liquid in the chapter Mixtures?

We filtered the water and sand through a paper towel to remove the sand.

Filtering is a good way of removing insoluble substances from water. Large pieces of insoluble substances can also be sieved out of the water.

Design, make and evaluate a filter

This is the first time that learners are doing a Technology project this year, in Gr. 6, so you will probably need to remind them of the Design Process which is followed in Technology Projects. The first part is identifying the need and in this project a scenario has been set where the Thunderbolt Kids are planning a camping trip and have invited the Gr. 6 class to come with them. However, there is no clean drinking water at the campsite they want to go to and they cannot carry enough water for everyone for the whole trip. Use this scenario to construct the need to design a filter to take with them on the camping trip.

We follow the pattern IDMEC in the Design Process.

I stands for Investigating the problem which some people have, investigating existing products, and investigating concepts and skills that you will need to solve the problem, i.e. purifying water. Encourage learners to investigate filtering methods such as using sand, cotton wool and charcoal.

D stands for Designing. That means using what you have learnt from investigations to think of good ways to design a filter.

M stands for Making. When you make your filter, you use the materials and tools to make the filter according to the design. Notice that most children design with their hands, not only with pencil and paper. As they work with materials they get more ideas, and their design improves. So we should think of designing and making as more or less the same stage of a project.

E stands for Evaluating. After you have made your filter to solve the problem, you have to ask, does it work? Could we do a better one? During this phase, take all the learners outside and get them to hang their filters up and test them out by pouring a cup of muddy water through.NB. Make sure learners DO NOT drink the water. Rather compare the water before and after filtering to see if it has been purified. Prepare a big bucket of muddy water which you can scoop cups of water out of to purify. That way you will have some water left over to compare the filtered water to, to see if the learners' filters did purify the water.

C stands for Communicating. You must show other people how you decided on your solution to the problem. You need to write and draw your ideas. (The learners should be drawing and writing all through the project. Do not leave the writing until the end, because they find it boring at that stage. When they are getting new ideas they often enjoy writing because they are writing about their own ideas; this is a great strength of Technology in school. A Technology project gives the learners reasons for reading and reasons for writing. As a result, we can address the literacy problem through the subject of Natural Science and Technology.)

The Thunderbolt Kids are planning a camping trip and they have invited you and your classmates to come with them. They have all the equipment such as tents, sleeping bags and mats. The only problem is that there is no clean drinking water at the campsite. For such a large group, the Thunderbolt Kids cannot take enough bottles of clean water. So, Tom has decided that the group should build a filter to purify the muddy water from the nearby stream. But, they do not know how! We need to help them design and build a filter to purify the water on the camping trip.

DESIGN BRIEF:

A Design brief for a Technology project is a short statement of what you are going to make, why you are going to make it and what you are going to make it for.

Write a short statement where you state what you are going to be designing and why.

Your filter has the following specifications:

The filter must be able to filter a cup of muddy water and the water which comes out must be cleaner than the water that went in.

The filter must be able to hang up, for example from the branch of a tree.

You must be able to use it outside.

Your filter has the following constraints:

You cannot make the filter at home, you must make it in class.

You are confined to using as many recyclable materials as possible, such as 2 litre plastic bottles, plastic bags, etc.

INVESTIGATE:

We now need to do some more investigating about how to purify water. We saw how to purify water using a still and evaporation. But what are the ways to purify water using a filter. Do some research on the internet and in books and answer the following questions.

What types of filters can you make?

What materials do these filters make use of?

What is the purpose of each of the materials used to filter? For example, are some materials there for filtering large particles and some for filtering small particles? If so, which one is which?

DESIGN:

Now start designing your filter! Answer these questions before you start drawing your design.

What kind of filter are you going to design?

What size and shape will your filter be?

What recyclable materials could you use?

How are you going to hang it up, for example from the branch of a tree?

How will you collect the water that has been filtered?

Use the space below to draw a design for your filter. Remember to label the different parts and show which materials you are going to use. Leave some space to do a second drawing as you might come up with a better design as you are making your filter and see ways to improve it.

MAKE:

Now that you have a design, it is time to make your filter according to the specifications and constraints. Once you have all made your filters, you need to test them out to see if they work.

Do the testing outside. Show the class how your filter works and pour a cup of muddy water through the filter and collect the water which comes out.

DO NOT DRINK THE WATER as you do not know if you have completely purified the water. To further purify the water from the filters, you can also do a solar distillation using the still you made in the last activity to remove solids, and finally followed by boiling.

EVALUATE:

After you have made your filter, you have to ask, does it work and could you do a better one?

Compare the water before and after filtering. Was the water cleaner after filtering?

Which impurities did your filter remove - big or small or both?

How much filtered water were you able to collect from your filter? Was it the same amount that you poured in?

Did your filter leak anywhere? If so, how could you prevent it from leaking?

Do you think you could further purify the water you filtered by passing it through your filter again? Try it out and see if this makes a difference.

How could you improve your design?

What further steps could you take to purify the water which comes out of your filter.

Purifying water while hiking (video) http://video.about.com/camping/Purify-Water-on-a-Hiking-Trip.htm

You could do a distillation using the still made in the previous activity, and finally followed by a boiling step.

COMMUNICATE:

The last part in the Design Process is to communicate what you designed and made to others so that they can also learn about what you did, and learn from you. Write a paragraph below where you tell Tom about the filter that you designed and made to take on the camping trip to purify the muddy water in the stream. Tell Tom what you found that worked and what did not work and anything that you would change.

How is water cleaned by municipalities?

Do you have running water in your home? If you have, you are very fortunate, because many South Africans do not.

Fun activity to get you thinking about water, and where it goes once we have used it http://www.cleaninginstitute.org/clean_living/the_bubble_path.aspx

Clean water coming out of the tap http://www.flickr.com/photos/wwarby/4916577404/

South African municipal water is generally clean and fresh, and safe to drink. How does it get that way? This section tells the story of how water is treated.

The water from a tap does not start out clean and fresh. It may come from a river or a dam, or it may even be waste water that was used by a community or in a factory.

The process of cleaning the water is called water treatment, and the place where it happens is called a water treatment plant.

So what exactly happens at a typical water treatment plant?

There are five steps (or processes) in the treatment of water. The five processes commonly used to treat water are screening, sedimentation, aeration, settling, and disinfection.

Let us look at them in turn.

STEP 1: SCREENING

The raw water that arrives at the plant may contain dirt, fish, rubbish, plants and even sewage.

These things are screened out as the water flows into the plant. This means that the water passes through a screen (which is very much like a large sieve), and the solid matter stays behind on the screen.

After the screening step the water is still dirty, but the large pieces of rubbish have been removed.

STEP 2: SETTLING

During this step the raw water is allowed to stand in a large tank called a settlingtank.

What happens to the dirt when muddy water stands for a long time?

It sinks to the bottom.

When the raw water stands in the settling tank, the medium-sized pieces of solid matter (called sludge) sink to the bottom of the tank.

The raw water at the top is still dirty but now it only contains small pieces of solid matter. The bits of solid matter left are small enough for small organisms (such as bacteria) to eat. This is what happens in the next step of the treatment process.

STEP 3: AERATION

The raw water now flows into a special tank that contains bacteria. These are useful bacteria, because they help to break down the last little bits of solid matter as well as breaking down any natural soluble pollutants.

Since bacteria need oxygen to stay alive and healthy, air is bubbled through the water. This process is called aeration, because the name comes from the word 'air'.

STEP 4: FILTERING

Next, the water flows through a special filter made of layers of sand and gravel, just like the one you designed, only much bigger. The gravel layer of the filter is about 30 cm deep and the sand layer is about 1 m deep! The filtering step removes any remaining particles and most of the bacteria left in the water.

After this step the water is clear, but some germs and bacteria from STEP 3 may still be in the water. Remember that germs and bacteria are small enough to pass between the gaps between sand and gravel.

STEP 5: DISINFECTION

During disinfection, chemicals are added to the water to kill any surviving germs.

Resources about water http://www.partstap.com/ground-water-and-drinking-water-an-expert-guide-for-kids.aspx

Clean water is important for people, plants and animals.

Water can be cleaned by processes such as sieving, filtering, settling, decanting, boiling and adding chemicals to kill germs.

The water we use in our homes is cleaned before and after we use it.

What does it mean to purify water?

It means to clean water; to remove pollutants from the water.

What is clean water?

Clean water does not contain any pollutants.

Why do humans, animals and plants need clean water? Write a paragraph where you describe some of these needs.

Learner dependent answer. Water is necessary for life. We need clean drinking water for metabolic processes in our bodies and to replace water which is lost due to urination and excretion. We use water for washing and cooking and need clean water so that we do not become ill. Many animals make their homes/shelters in and around water and need clean water so that they do not become ill.

If you were not sure about the water that came out of the tap and you had a kettle, what would you do to the water to purify it? Why do you think this method of purifying works?

You could boil the water. This would kill any living microorganisms or bacteria in the water.

The woman in the picture is drinking water from the edge of a dam. What possible threats could she face from drinking this water without doing anything to purify it?

The water could contain disease-causing bacteria such as cholera, hookworm, bilharzia, typhoid, and it could contain chemicals or fertilisers from surrounding farmlands, etc.

Name the 5 steps in the water treatment process.

The five steps are screening, sedimentation, aeration, settling, and disinfection.

Do you think it is important to conserve water? Why do you think so? Write a paragraph to justify your answer.

Learner dependent answer.

Electric circuits

What is electricity?

How do we construct a simple electric circuit?

What are electric circuit components?

What is the function of each circuit component?

What is the difference between a closed and open electric circuit?

Use a Learning Cycle approach to teach Electric Circuits:

Engage: Assess the learners' prior knowledge by engaging them with either questions or a task related to the new concept to be learnt. The activities should provide an opportunity for learners to talk about their prior experiences with the concept.

Explore: The teacher provides a common activity, task or series of activities in which learners engage. Part of the exploration phase could be for learners to predict what they think would happen during an activity. The activities should provide learners the opportunity to collect and organise data that will allow them to generate explanations for the phenomenon under investigation.

Explain and reflect: The teacher leads a discussion around the learners' data. The teacher introduces vocabulary, ideas, concepts, etc. as necessary. The teachers and learners may co-construct an explanation for the phenomenon under investigation.

Elaborate or apply: The teacher provides opportunities for learners to extend their understanding by providing new and/or related experiences for them to apply what they have learnt.

Evaluate: Assess the learners' understanding of the concept/phenomenon through any appropriate manner.

A simple circuit

Many misconceptions develop in learners' minds about electricity and electrical phenomena if teachers are not careful about the correct use of scientific language and appropriate conceptual development of these ideas. Teachers speak, for example, too loosely about concepts like electricity, electric current and charge as if these concepts are the same thing. Learners were first introduced to electricity in Gr. 5 and this year the concept will be built upon much further.

If we think of the world that we are currently living in, one of the things that we encounter every day and almost everywhere is electricity.

electric circuit

electric current

component

device

appliance

battery

switch

What do you know about electricity?

In step 1 of the Learning Cycle, learners must brainstorm what they know about electricity.

Think about electricity and write your answers or responses in the spaces provided below.

QUESTIONS:

Name and draw five appliances in your home that need electricity to work.

Name five applications (uses) of electricity in your neighbourhood.

Name five applications of electricity in your school.

Why is electricity important to you?

Why is electricity important for your city or town?

Why is electricity important for your country?

You are building a brand new house. You want an electric stove in your kitchen. Name all the things that must be done for your stove to work.

Electric stove is connected to the electrical supply from a supplier like ESKOM, also called the mains supply. An electrician must install the connecting wires in the house.

Cellphones work with electricity. How does your cellphone make use of electricity?

Cellphone has a battery.

What is the difference between the way we can get an electric stove and a cellphone to work?

A cellphone works from a rechargeable battery. The stove is connected to the mains supply. The cellphone battery is recharged from the same electrical supply as for the stove.

What would you say electricity is?

Electricity is the name given to a wide range of electrical phenomena. It underlies in one form or another almost everything around us. It has applications in science, engineering and technology. It has to do with the physical phenomena associated with the presence and movement of electrically charged objects. Electricity includes a wide variety of well-known electrical effects, such as lightning, static electricity, electromagnetic induction and an electric current in an electric wire.

A simple circuit http://www.youtube.com/watch?v=INBYuA6KoLA

We are using electricity all the time. We need to understand what it is about and how to use it safely and correctly.

Have you ever used a flash light (torch)? What is it used for? How do you get the flash light to work? Let us try to get the bulb of a torch to work. We want to do this without using the torch itself.

How to get a light bulb to work

In step 2 of the Learning Cycle, learners explore how to construct a simple electric circuit by getting a light bulb to work.

Before getting the learners to do the activity, do it yourself and ensure that it works with the batteries and bulbs available. Some bulbs might need a battery of more than 1.5 V. The best would be to find bulbs that would work from 1.5 V. The wires could be obtained from any electrical appliance not used anymore. If you cannot find a bulb that would work from 1.5 V, then try a 9 V battery.

There is a YouTube video (8-9 minutes) that might be helpful to teach this unit.

MATERIALS:

D-size battery (1.5 V)

torch light bulb

three pieces of electric wire 15-20 cm long with the ends about 1 cm stripped of the plastic insulating material

adhesive tape or Prestik

piece of cardboard

two thumbnails with metal (brass) tops (remove plastic if tops are covered)

a metal paper clip (remove the plastic if covered)

INSTRUCTIONS:

Electrical contact is important in all the activities that follow. If the connections or switches do not work later on, ensure that there is electrical contact (metal on metal) at each contact point in the circuit. Take care to indicate this to the learners as well.

Work in pairs.

The pictures below show four ways of connecting the battery and the bulb using only ONE wire.

First predict if the bulb will light.

Then do the connection and test if your prediction was correct.

Circuit

Prediction - Will the bulb light up? (Yes or no)

Experiment - Did the bulb light up? (Yes or no)

No

No

Yes

No

It is NOT important for learners to get the predictions correct! This is part of a learning process that works towards conceptual understanding and coherence. However, predictions are based on some reasoning, and so it IS very important that they are allowed to reflect on why their predictions were incorrect. Many learners leave the school system believing that predicting is guessing with no follow-up.

How many other ways can you light the bulb? Try different connections. Draw those that work and those that do not work in the table below.

Learners might come up with more connections that do not work rather than connections that would work. The bulb could be put on the negative side of the battery as well to get a connection that can work.

Connections that work

Connections that do not work

Describe in words what you did to get the bulb to light.

Teacher note: The core objective here is to form a complete path for electricity that connects one terminal of the battery to one terminal of the light bulb and the other to the other.

You have just constructed a simple electric circuit! Let us now see if you can also find a way to light the bulb using two wires.

The next pictures show four ways of connecting the battery and the bulb with TWO wires.

Use adhesive tape or Prestik to keep the wires attached to the battery. Do the same as before:

First predict if the bulb will light.

Then do the connections and test if your prediction was correct.

Circuit

Prediction - Will the bulb light up? (Yes or no)

Experiment - Did the bulb light up? (Yes or no)

No

Yes

No

No

Try some more ways to connect the battery and the bulb with two wires. Draw one example of a setup that worked and one that did not work.

Set up that works

Set up that does NOT work

You have constructed another example of an electric circuit!

Describe in words what you have done to get the bulb to light in the case of using two wires.

In step 3 of the Learning Cycle, a discussion should follow. Introduce some of the vocabulary, ideas and concepts. Together with your learners you must co-construct an explanation for the phenomenon under investigation (why the electric circuit works or does not work).

Now that we have investigated different ways of making a simple circuit, let's define it in more detail.

Electric circuits have different components. What does 'component' mean? Look up the definition for component in your dictionary and write it below.

A part or element of a larger whole, especially a part of a machine or vehicle.

A simple electric circuit has at least three components:

A source of energy, such as a battery.

Conducting material, such as the electric wires.

A device that transfers the energy for a useful purpose, such as the bulb that provides light.

Note that the diagram has an additional component: a bulb holder. Be aware that this obscures the actual connections to the bulb.

A simple circuit

Do you think there is something flowing through the bulb when it lights up? When we connect the bulb so that it lights up there is something flowing through the whole circuit. When it does not light up, we have not made a proper or complete pathway for electricity. This flowing `thing' is called electric current. If the bulb lights up, we say there is an electric current in the circuit. The electric circuit is a system for transferring energy. Think again about the circuits that you have constructed so far.

What are the conditions for the bulb to light up?

The circuit should have at least all three components as mentioned above. The circuit should be closed. The connections should provide electrical contact (metal on metal).

Let us look at the torch once more:

Is the bulb providing light all the time?

When does it provide light and when not?

What do we call the component of the flashlight that allows us to turn the light on and off?

A switch is used to put an electrical device on or off. But how does it work?

This is a typical torch - the big red button is the switch.

Simulations to build simple circuits http://phet.colorado.edu/en/simulation/signal-circuit and http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

Investigating how a switch works

MATERIALS:

a paperclip

two thumbnails (drawing pins)

a piece of cardboard

a torch bulb

3 pieces of wire

batteries

INSTRUCTIONS:

To make the switch, bend the paper clip as shown in the diagram.

Pin the ends of the two wires down on the cardboard with the thumbnails. One of the thumbnails should also pin down the paper clip.

The other end of the paper clip can be moved to make contact with the second thumbnail or not.

Move the paper clip away so that it does not make contact with this thumbnail.

The switch

We now want to use the switch. Use the same setup for a simple electric circuit with a bulb, battery and 2 wires as you did in the last activity.

Connect the paperclip switch to the battery by using a third electric wire. Remember to keep the wire ends in position with cellotape or Prestik.

The setup with the switch and simple circuit

QUESTIONS:

Move the paper clip onto the second thumbnail. What happens?

The bulb lights up.

Move the paper clip away from the second thumbnail? What happens now?

The bulb goes out.

Explain why you think the paper clip and cardboard device can be called a switch.

We already said that a switch is used to turn an electrical device on or off. We can also say that a switch is used to close or open an electrical circuit. When the switch is on, the circuit is closed. An electric current then exists in the circuit. We could also say there is an unbroken electric pathway in the circuit.

When the switch is off the circuit is open. In this case there is no electric current in the circuit. The electric pathway is now broken.

Making a battery from a lemon (video) http://www.youtube.com/watch?v=AY9qcDCFeVI

Name four other electrical appliances in your home that has a switch.

Circuit components

We need to have a closer look at the components in the electric circuit. This will help us to understand how a circuit works.

For the following activities, it is best if learners can see the actual components mentioned (different batteries, light bulbs, etc), but if that is not possible, then make reference to the photos included to complete the questions. This will help learners to realise that the circuits they are building in class represent bigger circuits that are all around them in their daily lives, whether it is the circuit in a car or a circuit in a house or the classroom when you turn on the light.

Batteries come in all shapes and sizes

MATERIALS :

a selection of different batteries, such as:

a torch battery

a watch battery

a cellphone battery

a hearing aid battery

a car battery (or photo)

INSTRUCTIONS:

Look at a typical torch battery.

Describe in words what the battery looks like. Refer specifically to the ends of the battery.

The battery is shaped like a cylinder. One end is flat, and the other end has a knob. The battery is covered in a metallic material.

Look carefully to see if you can identify a positive (+) and a negative (-) sign on the battery. Which side of the battery is marked with a positive sign and which side with a negative sign?

The side with the knob is the positive end, and the flat side is the negative end.

Below is an image of a typical torch battery. Indicate on the image which is the positive and which the negative pole of the battery. Use a (+) and (-) sign as you have seen it on the battery.

Batteries come in all shapes and sizes. Look at the pictures below of different batteries.

Different sized and shaped batteries

You may be lucky enough to have different types of batteries in your class, such as from a watch, a cellphone or a car. If not, ask an adult in your family to show you a car battery, a cellphone battery and a battery used in a watch after school.

Draw sketches of such batteries below. Indicate on each sketch the positive and the negative pole of each kind of battery. Below are some photos to help you if you cannot find these batteries.

Car battery

Cellphone battery

Watch battery

A car battery

Watch batteries: these are quite small!

For some appliances it is very important that the batteries are put correctly into a specific position. Why do you think this is the case? This is because the battery is used to get an electric current in the appliance and in some appliances the electric current can only go in a specific direction through the appliance. To prevent the appliance from being damaged, the battery must be inserted in the correct direction.

Investigating bulbs

MATERIALS:

a torch bulb used in the simple circuit activity

a light bulb for a house fitting

INSTRUCTIONS:

Compare the bulb that you used for the circuits with a light bulb that is used in a light fitting in a house or in your classroom. Below is a close up of a light bulb used in a house fitting if you do not have an actual one.

A light bulb

Try to identify the following six parts of the bulb: glass cover, bottom metal casing, two metal pins, very thin wire between the metal pins, glass piece that keeps the metal pins in position and a metal contact point at the bottom. Label all parts of the bulb on the sketch below.

In 1879, just over 130 years ago, Thomas Edison invented the first light bulb. Think of the all the changes it has brought to our world today!

Assume the bulb is connected to a battery. Use a bright colour pencil or pen (red if possible) to draw the path of the electric current through the bulb.

The path should start at the metal casing, then up one of the metal pins, then through the thin wire, then down the other pin to the connection point at the bottom of the bulb.

We know now that a bulb lights up when it is connected correctly to a battery. Where in the bulb does the light come from?

The thin wire between the two metal pins.

How does the glass cover feel after the bulb was on for some time?

Hotter than before.

There are also other kinds of light emitters: Fluorescent, LEDs, halogen lamps, etc. See if you can identify what type of lights are used in your classroom.

The battery is the source of energy. Some of the energy is transported through the electric wires to the thin wire inside the bulb. The thin wire becomes hot and emits (gives off) light. From the thin wire, the energy dissipates to produce heat and light. So, chemical energy from the battery is transferred to the bulb to provide light and heat.

Let's look more at electric wires

MATERIALS:

conducting wires

Make sure the insulation has been stripped off the ends of the wire so that the metal wire is sticking out of the end of the wire.

INSTRUCTIONS:

Look carefully at the end of a piece of electric wire, or else look at the photo below.

Examine the inside and outside of the wire.

The end of this wire has been stripped of the plastic.

QUESTIONS:

What are the two materials shown in this photo?

Inside: copper wire, Outside: coloured plastic material

Why does the wire have different materials on the inside and the outside? What are the functions of the inside and outside materials?

Inside: Copper wire is an electrical conducting material. It allows a path for an electric current in a circuit. Energy is transported in the copper wire from a battery to a device. Outside: Coloured plastic is an electrical insulating material. It prevents the transfer of energy to the environment. It is also there for safety purposes to prevent damage or shock if the electric current is large.

We have already discussed and constructed a switch, but a light switch in a house looks a bit different..

A light switch

Describe in words how you think a light switch in your house works. Hint: look again how we made a switch with a paper clip.

When you flick the switch on, a connection is made (and the circuit is closed) meaning the light bulb will light up. When the switch is turned the other way (off), then the connection will be broken and the circuit will not transfer energy, meaning the light bulb will not light up.

Circuit diagrams

If we want to keep a record of how we constructed a specific electric circuit, we can take a photo of it. If we do not have a camera, we can remember the circuit by drawing a sketch.

Look at the sketch below of the circuit that you made in the activity with the paperclip switch.

A sketch of the simple circuit with a paperclip switch, battery and bulb

It takes time to draw a sketch like this. It will even take longer if we add more components to a circuit. We could have more than one bulb like in the case of all the lights in your home. There could be also more than one switch. Each light in your home has its own switch.

All of us do not draw equally well! To save time and to avoid bad sketches, scientists came up with a way of representing the components of a circuit with special symbols. These symbols are used all over the world. It helps scientists, engineers and technicians to draw or record circuits more quickly. It also helps everybody to understand the circuit in the same way.

The table shows the sketch and the symbol for each of the components of our circuit.

Component

Sketch

Symbol

Battery

Bulb

Electrical wire

_____

Switch

Open switch, circuit open:

Closed switch, circuit closed:

REMEMBER: a battery is made up of chemical cells. Sometimes people refer to batteries as cells, but in this book we will mostly use the term battery or batteries.

When we put these symbols together to represent an electric circuit, we call it a circuit diagram.

Draw a circuit diagram of the sketch above. Use the symbols in the table in place of sketching the components.

Compare your diagram with the one below. You might have drawn a diagram like the one below.

Take note that for electric circuit diagrams we represent the wires with straight lines.

This is a simple and quick way to represent an electric circuit and it should be clear to everyone that this circuit has a battery, a bulb and a switch, all connected with electric wires. Although we draw the wires as straight lines in a circuit diagram, remember that in real life, the wires are not straight. Just think of the electric wires that are attached to the appliances in your home, like to a kettle, a lamp, a vacuum cleaner or a computer.

Swap the components

Teacher note: In step 4 of the Learning Cycle, the teacher provides opportunities for learners to extend their understanding by providing new and/or related experiences for them to apply what they have learnt.

MATERIALS:

circuit components (battery, wire, bulb, switch)

INSTRUCTIONS:

Think again about our electric circuit and the diagram above. We have the battery on the left, the bulb at the top and the switch at the bottom.

Assume we swap the bulb with the battery. The bulb is now on the left and the battery at the top.

First of all, draw the circuit diagram for such a setup.

Predict what will happen if you close the switch.

The bulb will light up with the same brightness as before.

Set up the circuit like this with the components you used before. Put the switch on and check if your prediction was correct. What do you conclude? Does it matter where in the circuit we position the components?

The sequence of the components in a simple circuit like the one used here is not important. The electric current will be the same in either case, since we did not change the battery (same power supply) or the bulb (same resistance).

Let's now practise drawing circuit diagrams.

Drawing circuit diagrams

INSTRUCTIONS

For each of the following, draw a circuit diagram in the space using all the components that are listed.

A circuit with 1 cell and 2 bulbs

A circuit with 2 cells and 2 bulbs

A circuit with 3 cells and 3 bulbs

A circuit with 3 cells, a bulb and an open switch

A circuit with 1 cell, 2 bulbs and a closed switch (the switch must be in between the bulbs)

More than one possible circuit can be drawn here. The given ones follow certain entrenched conventions. There is no reason why circuit 4 for example can't have alternating batteries and bulbs. The learners can even be asked to construct this circuit and observe if there is any noticeable difference in how the light bulbs behave. If they behave as before there is no real difference between the two circuits even though the connections are different.

1:

2:

3:

4:

5:

An electric circuit is a system for transferring energy.

A circuit is a complete and unbroken pathway for electricity.

A simple circuit is made up of different components (a source of energy, conductors and a device).

A circuit can have a switch to turn it on or off.

Electric circuits can be drawn as circuit diagrams using symbols.

In step 5 of the Learning Cycle, the teacher assesses the learners' understanding.

Explain in your own words what an electric circuit is.

An electric circuit is a system for transferring electrical energy. It is a complete, unbroken path for electricity.

What is the function of each electrical component in the table below?

Component

Function

Electric wire

Battery

Switch

Bulb

In which of the following electric circuits will the bulb glow? Write yes or no next to each diagram. Write down a reason for your answer below the circuit.

Yes or no:

Yes or no:

Reason:

Reason:

Yes or no:

Yes or no:

Reason:

Reason:

Draw a circuit diagram of the circuit shown below.

Look at the following circuit diagram. Write down all the components represented in this circuit. Include the number of each component as well.

Two cells, two bulbs, a switch and 4 connecting electric wires.

The circuit diagram in question 5 represents a real circuit. In the real circuit, are the bulbs lit up? Why do you say so?

Yes, they are as the switch is closed.

Symbolic representation is new to learners at this level. Make it explicit that when we say `in the above circuit' we really mean 'in the actual circuit that this is a diagram of'.

Look at the following circuit diagram. The bulb does not light up for four reasons. Draw a circle around the parts of the circuit that prevent the bulb from lighting up. Give a reason why the bulb doesn't light up in each case.

Batteries: one battery `pushes' current one way, the other the other way, so no current

Switch: open so current can't pass through it.

Light bulb: only one terminal connected to circuit, so no current can pass through it

Gap in circuit: no current can pass through it.

The circuit diagram in Question 7 represents a real circuit. Use the space below to draw what the real circuit might look like, if all the problems with the circuit were sorted out.

Electrical conductors and insulators

What does it mean if something conducts electricity?

What is the difference between an electrical conductor and insulator?

Why are insulators important?

We use electric wires in electric circuits. Did you have a close look at the wire? Did you notice what materials are used on the inside and outside of the wire? We should also know why two different materials make up an electric wire.

What are conductors and insulators?

We can say that a material or object conducts electricity or it does not. But what does this mean? Let's do an investigation to find out. To do this we are going to use a simple circuit. We will connect pieces of different materials into a closed circuit with a light bulb in it. We can easily see if the material is a conductor.

conductor

insulator

How will you know if the material in the simple circuit conducts electricity?

The bulb will light up.

What kind of materials can we use in electric circuits?

One cannot investigate materials with low but significant conductance such as salt water. Later there is reference to shocking and the dangers involved. The reason we get shocked is because we are pretty good conductors. This is mostly due to the fact that our bodies have a fair amount of salt in solution. Also, pure water is a very poor conductor and poses much less of a shock risk. In this investigation, some substances, such as salt water, cannot be tested (unless many batteries are connected in series to the test circuit).

AIM:

Write down an aim for this investigation.

To investigate if materials have conducting or insulating properties

MATERIALS AND APPARATUS:

D-size battery (1.5 V)

torch light bulb

three pieces of electric wire 15-20 cm long with the ends (about 1 cm) stripped of the plastic insulating material

adhesive tape or Prestik

various objects made of different materials like:

metal paper clip (remove the plastic if covered)

paper clip covered with plastic

rubber band

nail

glass object (rod, tube or just a piece of glass)

pen

coins (brass and silver)

cardboard

paper (fold the paper to form at least 4 layers to make it easier to connect in a circuit)

steel wool

piece of wood

pencil (contact points on the wood)

pencil with both sides sharpened to expose the lead, test the lead part of the pencil

rubber

chalk

piece of ceramic

aluminium foil

metal spoon

plastic spoon

piece of leather

drinking straw

styrofoam

Learners can work in pairs, or groups of 3-4. The idea is to investigate different types of materials first to see if they conduct electricity or not so that learners come to the conclusion themselves that conductors are normally metals, and insulators (non-conductors) are normally non-metals.

METHOD:

Use three electrical wires to set up the electric circuit as shown below. Note that the ends of two of the wires are not touching. What do we call such a circuit?

open circuit

Draw the circuit diagram for the circuit shown in the sketch in the space on the right of the sketch.

Sketch

Circuit diagram

Test that the circuit is connected properly by touching A and B to each other and making sure that the bulb lights up/

Take the first one of the objects in the list above. Put the object between the two wire ends at A and B.

The sketch below shows how to do it. Make sure there is good contact between the object and the wire ends.

Make sure learners only touch the ends of the wire to the object and do not touch the object themselves with their hands while they are completing the circuit, to prevent breaking the electric circuit.

Test each object as shown here with the nail.

Does the bulb light up or not? Write the name of the object in the left or right column of the table below, depending if the bulb lights up or not.

Repeat for all the other objects in the list.

Some objects are composites of conductors and insulators. The visually different parts should be tested as well. For example, a knife may have a plastic handle, so test the handle as well as the metal blade.

RESULTS AND OBSERVATIONS:

Record your results below

Bulb lights up

Bulb does not light up

What do the objects that lit up the bulb have in common?

All the objects that lit up the bulb are made of metallic materials. The lead core of a pencil (graphite) also conducts electricity. Some metals are better conductors than others.

What do all the objects that did not light up the bulb have in common?

They were all made from non-metals, such as plastic, wood, glass, ceramics, etc

Some metals are better conductors than others. If the bulb does not light up with some metallic objects, it might be that the current is very small. Try an LED in this case to show that there is a current. Be careful! Remember that an LED only conducts in one direction. It should be connected correctly in the circuit: positive terminal of the LED connected to the positive terminal of the battery.

CONCLUSION:

Write a conclusion for this investigation below.

Metals conduct electricity and non-metals do not conduct.

If the circuit is closed, the bulb lights up. We have learnt before that in such a case there is an electric current in the circuit. A material that allows a path for an electric current is called an electrical conductor. The material conducts electricity.

What type of materials did not light up the bulb?

mostly non-metallic materials

Although the circuit seems closed, the bulb did not light up. What does that mean?

There is not an electric current in the circuit.

In this case the path for the electric current is broken. We call a material that does not allow a path for an electric current an insulator.

Good electrical conductors and insulators

A good electrical conductor is a material or substance that allows an electrical current to pass through it easily. We call the ability to conduct conductivity. Electrical conductors are usually metal because metals generally have high conductivity. Copper is one of the best electrical conductors and this is why it is the most common material used for electrical wiring. Gold and silver are even better conductors than copper, but they are very expensive and only used sometimes.

Insulators are non-conducting materials that do not easily allow current to pass through them. This does not mean that current can not pass through them at all. For example, we generally consider air an insulator, however, lightning can cause electric current to pass through air. Similarly, rubber gloves and shoes will protect you from mains electric current, but not from lightning. Examples of insulators are plastic, rubber, and wood.

When two conducting materials make contact, electricity can pass through them. Our bodies are also good conductors of electricity. This means electric current can easily flow through you and into the Earth, giving you a shock. That is why we cover conducting wire with insulating materials (like the plastic around extension cords). We want to protect ourselves from being shocked, and prevent the electrical current from passing to other conductors.

The importance of electrical insulators

Think of the electric wires that you use in class for the activities. Why do you think they are covered in plastic? The plastic is an insulator and therefore prevents you from getting a shock. The plastic coating acts as a barrier that prevents you from getting a shock, allowing you to handle the wire when the circuit is on.

Electrical insulators are also used in other places. Have you ever looked up at power lines or telephone lines? You will see that the poles that carry the lines are sometimes made of wood. Wood does not conduct electricity so the electric current can therefore not get from the wires into the pole.

Sometimes you will also see little white or coloured caps holding the wires as in the photo below. These caps are made of ceramic which also does not conduct electricity.

In this photo, the wooden poles and white ceramic caps are electrical insulators.

Sometimes, it is especially important to have ceramic electrical insulators between two different metal conductors to prevent electric current from flowing between the different parts such as in the photo below.

Can you see the dark red-brown ceramic electrical insulators?

You can also point out the electric rings in the photo which are also electrical insulators and a further precaution.

Do you remember naming the different parts in a bulb? Look at the picture of a bulb again below and explain why you think the piece separating the electric metal pins (conductors) is made of glass.

The glass is an insulator and therefore prevents electric current from flowing through the bottom of the electric pins and not through the coil at the top. With the glass insulation, the electric current rather flows through the coil at the top which then heats up and produces light.

Electricians are people whose job it is to work with electricity and fix the wiring in houses and other buildings. Electricians often wear rubber gloves to protect themselves from getting a shock. Rubber is an electrical insulator.

Some materials allow electric current in them. They are called conductors.

Some materials do not allow electric current in them. They are called insulators.

Metals are usually conductors and non-metals are usually insulators.

Electrical insulators have important functions like insulating wires or protection from electrical shock, e.g. an electrician's rubber gloves.

Suppose you have found a piece of material. You are not sure what the material is. You want to find out if it is a good conductor or a good insulator. Describe in words what you would do to determine if the material is an electrical conductor.

Set up an electric circuit as was done in the investigation with a battery, a bulb, and electric wires. Two ends of the wire must be unconnected so it is an open circuit. Test the object/material by placing it between the two ends of the wires to complete the circuit. If the material is an electrical conductor then the bulb will light up.

What is the difference between an electrical conductor and insulator?

An electrical conductor allows electric current to flow through it (it will complete an electric circuit) and an electrical insulator does not allow electric current to flow through it (it will not complete an electric circuit).

What kinds of materials are used to make electric wires? What are the functions of the materials?

A metal such as copper is used to make the inside of the wire as copper conducts electricity. The copper wire is covered in a material such as plastic which is an insulator to protect people handling the wire and also prevent the wire from making an electrical connection with other metal objects.

Why are insulators important?

Insulators protect people from electric shock; in some cases from possible death. Insulators also protect appliances from damage.

List five insulating materials.

Glass, plastic, wood, ceramics, rubber, chalk, paper, cardboard, etc

Look at the owl sitting on the pole below. Why does it not get an electric shock from the powerlines?

An owl perched on a pole http://www.flickr.com/photos/vhhammer/6567396763/

The pole is made of wood which does not conduct electricity and there are ceramic caps between the power lines and the pole which act as further insulators.

The man in the following picture is setting up an electric generator. Why is the man wearing gloves while he does this? Why is he also wearing boots with thick rubber soles?

This man is wearing gloves. http://www.flickr.com/photos/editor/72550973/sizes/l/

He is wearing gloves made of material and rubber as they are electrical insulators and therefore protect him from getting an electric shock when handling electrical wires and appliances. The thick soles on his shoes also prevent an electric current from passing through him and into the Earth.

Systems to solve problems

How can we use electric circuits to make useful devices and appliances?

What happens to energy when we use electrical devices and appliances?

This unit is mostly application of what has been learnt before. Develop some of the science process skills: observe, design, evaluate and communicate. In order to develop thinking and motor skills, give the learners a project to build a model of a house that includes electrical wiring.

Using electric circuits

Electric circuits are used all around us, for example in lights in our homes, streets and shops. Let us imagine our world of today without electricity!

system

energy transfer

A world without electricity

Let the learners work in groups of 2-4. There are no specific right or wrong answers here, except if the responses do not have anything to do with electricity. The learners are giving their perceptions and opinions. The activity provides a starting point for learning about the use of electric circuits.

INSTRUCTIONS:

Write a short paragraph of how our world would be like without electricity.

Describe the three things that will be the biggest disaster for you if there was no electricity.

Would there be any advantages of not having electricity? Discuss this with your classmates and write your answer below.

Your group should now compare the advantages and disadvantages of electricity. What is the group's conclusion, a yes or no for electricity? Write down your group's reasons for saying yes or no.

Electric circuits are often used to solve a problem where we need energy. A battery or mains supply is a source of energy. The energy is transported to a device or an appliance using electric wires. The device or appliance dissipates the energy. The effect could be light, sound, heat or movement. In other words, the device gives off energy in the form of light, sound, heat or movement.

A system is something that consists of different parts working together to form a whole. In an electric system, there is an input (energy) and an output (resulting in light, heat, movement, or sound). Let's look at some examples of electric systems where we use the output energy to do something useful.

Energy is transferred or dissipated, not transformed. Energy is defined as the capacity to do work, so it does not change from one form to another, but it can be transferred.

Electric circuits influence our lives

INSTRUCTIONS:

Look at the photos or sketches below.

Name the appliance or device.

Say what it is used for and what the energy is transferred to (light, sound, heat or movement)? In some cases it might be more than one thing!

http://www.flickr.com/photos/andybutkaj/1495901113/

Name:

Use:

Energy transferred from _______ energy to ____________

http://www.flickr.com/photos/54400117@N03/5069103310/

Name:

Use:

Energy transferred from _______ energy to ____________

http://www.flickr.com/photos/wonderlane/3134754840/

Name:

Use:

Energy transferred from _______ energy to ____________

Name:

Use:

Energy transferred from _______ energy to ____________

http://www.flickr.com/photos/39747297@N05/5229733311/

Name:

Use:

Energy transferred from _______ energy to ____________

Name:

Use:

Energy transferred from _______ energy to ____________

Name:

Use:

Energy transferred from _______ energy to ____________

Name:

Use:

Energy transferred from _______ energy to ____________

Name:

Use:

Energy transferred from _______ energy to ____________

(Scalextric http://www.flickr.com/photos/magickevin/7161372557/)

Name:

Use:

Energy transferred from _______ energy to ____________

http://www.flickr.com/photos/tonythemisfit/3052219034/

Name:

Use:

Energy transferred from _______ energy to ____________

This is quite a long activity with many examples, but it leads into the Technology Project a bit later where learners have to use an electric circuit to produce light, movement, sound or heat. This activity will act as a stimulus for ideas for the project.

Each of the examples in the previous activity uses an electric circuit to provide us with energy where we need it, whether it is light on the street, sound for our radio, or heat in a building. Or even in some toys and models such as a car racing game, or model electric train set! We can say that electrical appliances can solve problems for us. They are able to transfer electricity so that another useful form of energy is released.

Be an electrical engineer or technician

engineer

At this point learners have learnt adequate concepts related to electricity to give them a Technology Design project to do. They can work individually or in teams of 3-4. Ideally though, each learner should design and make their own system to fully engage with the task. Learners will apply what they learnt by first discussing, designing and drawing a plan of how to use a circuit to produce movement, light, sound or heat. It is generally more difficult to produce heat energy using cells, but this can be explored by learners if they feel they are up to it. Then they will implement their design and make the structure and then present it to the class. Communication is a vital skill and forms part of the Technology Design Process. Communication can be written or verbal, but in this case learners must verbally present their designs to the class. The model that learners build need not be to scale. Possible designs include a steady hand game, a house (encourage them to have more than one room or a doorbell system), a lighthouse, or some type of toy which produces sound or movement. Encourage learners to use everything that they have learnt about electric circuits and include different components, such as switches.

Let's say you want to become an electrical engineer or electrician. One of the things that you will be doing is to design systems that use circuits to solve problems for people, whether it is the wiring in a house, an alarm bell, a lighthouse on the coast, or constructing toys which use electrical energy to work.

Design, make and present a system using a circuit

DESIGN BRIEF:

You are an electrical engineer and you need to come up with a design for an electrical system to solve a problem. You need to design and make a system that uses a circuit to produce movement, light, sound or heat. Write a Design Brief where you identify what you are going to make and why it needs an electric circuit.

INVESTIGATE:

The next step in the Design Process is to do some research about the instrument that you are going to make. You can use books and the Internet to do your research.

Answer these questions when doing research about your electrical system:

How is this system normally made?

What components does it need?

What type of energy will be produced from electrical energy?

Why do people need this system? What problem does it solve?

DESIGN:

Now that you know a bit more about the system you want to make you need to design how you are going to make it.

Your system has the following specifications:

The system must make use of an electrical circuit.

The system must produce either movement, sound, light or heat.

The circuit must make use of some of the components that you have learnt about, such as batteries, light bulbs, switches, buzzers, wires, etc.

Your system must make use of a switch to turn it on and off.

Your system has the following constraints:

You must make it in class.

You cannot get an adult electrician to design your project for you! You must come up with your own design.

Your system is not life sized, but must be a model.

Answer these questions:

What materials will you need to make it? For example, which electrical components will you need? Which other materials will you need, such as a cardboard box to put the system in, adhesive tape or Prestik, drawing pins, or paint to paint the box?

What tools will you need to make it? Such as pliers to cut the wire, scissors to cut cardboard. Make a list and collect some of these items from home, or else ask your teacher if he/she has any.

How many batteries will you need for your circuit?

Where will you place the switch? What type of switch are you going to make?

Now you need to draw some designs for your system. Use scrap pieces of paper to do your first designs. Once you are happy with your design, use the space below to draw your design. Label your drawing showing what materials you are going to use for the different parts.

When you are making your system you might get better ideas to improve the design as you test it out to see if it produces the required output. So come back afterwards and draw on the bottom half of the page; show what you really decided to make.

MAKE:

Now make your system! After you have all finished making your systems, perhaps go around and look at what others have done. Ask each other questions to see what you can learn from others. You will also have to present your project to the class so use this time to get ideas about how to present your idea and product that you made.

EVALUATE:

Before we get on to presenting the projects, you need to evaluate your own project. You can then use this evaluation in your presentation to show others what worked and did not work.

Does your system look like your initial design?

Does your system produce a movement, sound, light or heat?

Where would people use the system you designed to solve a problem in our daily lives?

Is there anything you might do differently to improve your design?

COMMUNICATE:

An engineer needs to be able to present their designs to show others what they have come up and communicate their ideas. Engineers can present a written report and hand in their design drawings. But, often an engineer will need to present the design and project by speaking and giving a verbal report.

Your last task in this Design project is to present your system to your class.

These are your instructions:

Present an oral report to the rest of the class to tell them about the system that you built.

You must have your system with you in the front of the class and show how it works.

You must explain the electric circuit that is used and what type of energy is produced.

Tell the class how your system could be used by people and why they might value your design. For example, could it be used in a house by people or maybe it could form a new toy on the market?

Lastly, tell the class what you learnt by doing this project and anything that you found tricky or difficult or that you might change if you had to do it again.

Each learner must be assessed for the actual system that they built and their designs, drawings and planning. And each learner must be assessed in the way that they present their project orally. Pay special attention to the learner's ability to project their voice and engage with the class, their ability to explain what they have done and whether they answered all the questions outlined in the instructions above.

Electric circuits solve problems like getting electric lighting for example.

There are many instances in the world around us where electric circuits are used, such as street lighting, alarms, electric gates, traffic lights, fans and heaters, some models and toys.

Name five things that we would not be able to do without using electricity. Explain why you think each of these things is important to us.

Learner dependent answer. Check that they have justified why each is important.

Jason builds an electric circuit that includes a bulb and battery for his bedside table so that he can read at night, but the bulb does not light up. List three things that could be wrong.

The battery could be placed the wrong way, the battery is flat, there is a break in the connection somewhere, one of the wires is not connected properly or is broken, the bulb may have `blown', meaning the filament inside the bulb is broken.

Jason does not want the battery in his bedside light to run out of energy. What could he do?

He can include a switch to turn it on and off to save the battery.

List three electrical devices that use energy from a battery.

Torch, cellphone, walkman, etc.

List three electrical devices that use energy from a mains supply.

Microwave, stove, iron, hairdryer, fridge, etc.

Draw an electric circuit diagram for the system that you designed and made in the Design Project.

Mains electricity

Where does mains electricity come from?

What are fossil fuels and how did they form underground?

Why should we save energy and how can we do it?

Why are illegal electrical connections so dangerous?

What is the difference between renewable and non-renewable energy resources?

This unit lends itself to searching for information, pictures, simulations and videos on the Internet, in the Library, in magazines and books. The basic information about the main topic is provided here, but teachers and learners should explore the topic further.

We are so used to switching on electrical appliances that we hardly think what makes it possible to have these things. Our focus turns to appliances that need a mains electrical supply. You have listed examples like a television, a computer, a kettle and many others before.

The big question here is `Where does mains electricity come from?'

Fossil fuels

A battery has stored energy which can provide electrical energy. However, our homes, schools, shops and factories cannot run on batteries because they cannot store or provide large amounts of energy. We use electricity every day. The main supplier of electrical energy is from power stations. We call this `mains electricity'. Power stations also need a source of energy to make electricity. In South Africa, this is mostly from fossil fuels.

fossil fuels

coal

oil

natural gas

power station

turbine

generator

renewable

non-renewable

What are fossil fuels?

Coal, oil and natural gas are fossil fuels. Some people think that fossil fuels are the remains of dead dinosaurs but this is not true! Actually, most of the fossil fuels we find today were formed millions of years before even the first dinosaurs. Fossil fuels were once alive!

Do you remember learning about fossils in Gr. 5 Earth and Beyond? Write down what you think a fossil is.

A fossil is the remains of a dead organism (plant or animal) from millions of years ago.

So fossil fuels are actually the remains of prehistoric organisms that lived millions of years ago!

Different fossil fuels come from different organisms and formed in slightly different ways.

How fossil fuels are made

Let's take a trip back in time, millions of years ago!

This activity is meant as a comprehension for reading appreciation. Ideally the learners should read the text themselves and then answer the questions that follow. The ability to read a lot of text, identify the main facts, and then answer questions or summarise text is an important skill.

INSTRUCTIONS:

Read the text below about how fossil fuels were formed and study the pictures

Then answer the questions that follow.

300 million years ago...

Think about what the Earth must have looked like back then! There were swamps and marshes everywhere and it was warmer than it is today. Ancient trees, ferns and plants grew everywhere. Very weird looking animals roamed the earth, and even stranger looking fish lived in the rivers and deep in the oceans and seas.

An ancient, prehistoric world

When these prehistoric plants and animals died their bodies their bodies decomposed just in the same way as organisms decompose today. The dead organisms became buried under layers and layers of mud, rock, sand and water. Over time, these layers built up and became very deep and they pushed down with a great pressure on the layers below it.

Millions of years passed, and the dead plants and animals slowly decomposed and formed fossil fuels. Different types of fossil fuels were formed depending on different factors. For example, whether it was the remains of plants or animals or a combination and how long the remains of the organisms had been buried for. The type of fossil fuels that formed also depended on the temperature and pressure conditions during the decay of the organisms.

Oil and natural gas

Oil is a dark, thick liquid that can be used to make petrol to burn in vehicles, such as cars, buses and trucks. Natural gas is colourless and it is used mostly in homes for heating and cooking food.

Oil and natural gas formed from organisms (plants and animals) that lived in the oceans before there were dinosaurs. When these organisms died, they settled on the bottom of the river bed or ocean floor and the layers built up under mud and sand (silt). The mud and sand slowly changed into rock and the rock and water pressure pushed down on the remains of the dead plants and animals.

Trilobites

Limulus

Ceratodus

Ammonoids

Over millions of years of being under heat and pressure, the dead plants and animals changed into a thick liquid, called crude oil. In deeper, hotter places tiny bubbles of natural gas formed. These were trapped under the rocks.

Over time, some of the oil and natural gas began to work its way up through the rock and to the Earth's crust and into rock formations called `caprocks'. Today, most of the oil and natural gas is collected from these caprocks by drilling down through the layers of rock.

Coal

Coal is a black rock that can be burnt to produce energy in power stations all over the world.

Coal was formed from the dead remains of trees, ferns and some other plants that lived 300 to 400 million years ago. This was when the Earth was mostly covered in swampy forests. These kinds of plants were very different to the plants that we get today. Over time, the layer of dead plants at the bottom of swamps was covered with layers of water and mud. The top layers squashed down on the dead plants. Over millions of years the heat and pressure turned the plants into the coal that we mine today.

Ferns were very common in the prehistoric world of plants. http://commons.wikimedia.org/wiki/File:Tree_Ferns_%28psd%29.jpg

Much of the Earth was covered in swamps millions of years ago.

The energy in coal originally comes from energy from the Sun. Plants on Earth used the energy of the Sun for photosynthesis and to grow. This energy was stored in the leaves, flowers and stems of the plants. As the plants died the energy was trapped.

QUESTIONS:

What are the three fossil fuels discussed in the above story.

coal, oil and natural gas

The organisms that fossil fuels were formed from lived many years ago and are different to the organisms that we get today. How many millions of years ago was this?

300 million years ago

The dead organisms are covered in sediments over time. Do you remember learning about sediments in Gr. 5 Earth and Beyond and how sedimentary rock forms? Write a description of what sedimentation is.

Sedimentation is when particles (either sand, rock, or organic material) settle on the bottom of a river or the ocean floor and over time form layers which begin to compact.

What are the two main factors which turned the remains of organisms into fossil fuels deep under the layers of rock and mud?

high pressure and heat

Explain why we say that all our energy originally comes from the sun, even in fossil fuels.

The organisms that fossil fuels are made from lived millions of years ago. The plants used the Sun's energy to make food by photosynthesis. When they died this energy was trapped in the plants' remains which then turned into fossil fuels. The animals that ate the plants got their energy indirectly from the Sun through the plants. When these tiny animals died, the energy was also trapped in their remains which became fossil fuels.

Do you remember learning about the states of matter in Matter and Materials. Each of the three fossil fuels discussed here is a different state of matter. Say what they are.

coal - solid, oil - liquid, natural gas - gas

The process of coal formation and natural gas and oil formation have similarities, but also differences. Draw a table where you compare these two processes. Give your table a heading.

Possible answers:

A comparison of the process of coal formation, and natural gas and oil formation (different fossil fuels)

Coal formation

Oil and natural gas formation

Millions of years ago that the organisms died to start forming fossil fuels

300 million years

300 million years

Organisms from which fossil fuel is formed

Plants (trees, ferns and other plants)

Tiny plants and animals

Place where organisms lived and died

Swamps

Water - mostly oceans and rivers

Layers that remains were covered in

Sand, mud, water

Sand, silt, water

Factors which contributed to formation

High pressure and heat

High pressure and heat

State of matter of fossil fuel formed

Solid coal

Oil - liquid, Natural gas - gas

Fossil fuel formation (video) http://www.youtube.com/watch?v=_8VqWKZIPrM

The way we obtain the different fossil fuels is also different. Coal is usually obtained by digging mines into the rock and sand to reach the coal deposits deep under the surface. This creates a huge hole in the surface of the earth as you can see in the photograph of a mine.

A coal mine http://www.flickr.com/photos/herry/35148275/

An oil rig in the ocean which sinks a drill into the ocean floor to reach the oil deposits

Oil and natural gas is obtained by drilling down through the rock. A hole is sunk with a huge drill so that the oil and natural gas can be reached and then brought up to the surface. This normally takes place in the ocean, as you can see in the oil rig in the photo.

Search the Internet to find out which countries in the world have large quantities of coal, oil and natural gas.

Search the Internet to find out which three countries in the world use the most fossil fuels.

Fossil fuels and electricity

The main supplier of electricity in South Africa is ESKOM. ESKOM uses mainly coal to produce energy for industrial and household use.

Let's look at a power station to find out how coal is used to produce electricity.

Look at the diagram and the steps which outline the process to make electricity from coal:

Coal is transported from a coal mine to a power station.

At the power station, the coal is ground into a fine powder (pulverised).

The ground coal then goes into a container where it is burned.

The heat generated from the burning coal is used to boil water in a huge boiler.

The boiling water produces steam that turns a turbine (a turbine is a big wheel which turns).

The turbine is linked to a generator which uses a coil to produce energy.

From the generator the electric current is transported ("carried") by a system of electrical transmission lines (also called power lines) and substations to our homes.

The process of making electricity from coal in a power station

Make a poster to trace the source of our electricity

MATERIALS:

poster size paper or cardboard

colour pens or pencils

INSTRUCTIONS

Design and make a poster for your classroom on which you illustrate the chain of objects and processes that allow us to use an appliance in our homes (such as a television set, stove or refrigerator).

Start with a picture or drawing of the Sun in the top left corner and end with the appliance in the bottom right corner of the poster.

Use arrows to show the sequence of objects and processes.

Label each object or process on your poster.

Decide on a heading for your poster and write it in big letters at the top.

The sequence should be something like sun \(\rightarrow\) plants and animals \(\rightarrow\) fossil fuels (coal) \(\rightarrow\) power station \(\rightarrow\) electricity \(\rightarrow\) delivery to home on power lines \(\rightarrow\) TV (or other appliance).

Fossil fuels are non-renewable resources of energy. This is because they take millions of years to form. Once these fuels are burnt, they cannot be recovered or reused. They are non-renewable.

A learner's conception of `millions of years' might not be well grounded. Fossil fuels are not renewable because we use them up far quicker (in a few centuries) than they can form (millions of years). This point will be lost if learners can not distinguish between hundreds and millions. This should be addressed by the teacher to focus on meaning of hundreds and millions.

The burning of coal produces billions of tonnes of carbon dioxide each year. Carbon dioxide is one of the greenhouse gases that contributes to global warming.

People on Earth are using up these deposits of fossil fuels much, much faster than they are being made as they take millions of years to be made! Look at the diagram of a power station again. Do you see the smoke that is given off when the coal is burnt? This causes huge environmental concerns as it is polluting our atmosphere. A bit later in this chapter we will look at other ways of producing energy which, unlike fossil fuels, are renewable.

Cost of electricity

infrastructure

expensive

kilowatt

Do you hear your parents and other adults talk about the cost of living? Do they remind you to switch off lights and other appliances that are not in use? Electricity is an expensive resource!

A learner might make the reasonable point that the coal is burnt anyway, whether you leave that light on or not. But, the point is to show that cumulatively, saving electricity can have an effect on reducing demand on power stations, and it also reduces the amount that your individual household spends on electricity if you use it efficiently.

Why is electricity expensive?

Electricity is costly because:

The production and delivery of electricity requires infrastructure (the structures and facilities) like coal mines, trucks and trains to transport coal, power stations, substations and wiring.

All of these buildings, structures, materials and processes are very expensive to build and maintain.

Some electrical appliances require a lot of energy, much more than others. For example, a geyser uses a lot of electricity to heat the water and so it becomes expensive.

When electrical energy enters your home, it must pass through a meter. Have you ever seen a white box outside your house? This is the electricity meter. A worker from the city council reads the meter so that they will know how much electricity you used. They then bill you for the cost. The more electricity we use, the more we pay and the more we use up fossil fuels. Some houses now have pre-paid electricity meters where you pay for your electricity before you use it.

This is an electricity meter. Can you see the number recording the electricity usage in kilowatt hours (kWh)? http://www.flickr.com/photos/hendry/397510397/

Running electrical appliances

We already mentioned that some electrical appliances use more electricity to run than others. Appliances that heat use the most energy, such as a geyser or heater. How do we know which electrical appliances use more electricity?

Energy required by electrical appliances and devices

This could be an individual task, each learner should look for this information so that they become familiar with looking for ways to save energy.

This is how we find out!

INSTRUCTIONS:

Find the appliances or devices listed in the table. If you do not have them in your home or school, ask family, friends or neighbours if you could look at theirs.

Have a look at each appliance and check for a label with information like the one below. This information is usually at the back or the bottom of the appliance.

230 V - 240 V; 50 Hz; 2 kW

Record the number that is followed by a W or kW on the label in column 2 of the table. This number indicates how much energy is required by the device in a certain time. It is called the power required by the device. We measure power in watt (W) or kilowatt (kW). The higher the value the more energy the device uses in a specific time.

Make the link between the unit W and kW where a kilowatt is 1000 watts. Similarly, metre (m) and centimetre (cm) and gram (g) and kilogram (kg). As well as metre and millimetre (mm) and ampere (A) and milliampere (A).

Add any other three appliances or devices to the list.

Record all the power values in column 3 in watt. If the power is given in kW, multiply this number by 1000 to get the value in watt (W).

For example: 2 kW × 1000 = 2000 W

If the device does not show a value in W or kW, look for two quantities given in volt (V) and milliampere (mA). Multiply these two numbers and then divide the answer by 1000 to get the power in watt.

For example: 240 V × 150 mA = 36 000 W

36 000 ÷ 1000 = 36 W

You divide by 1000 to correct for using mA instead of A. Power (W) = voltage (V) ÷ current (A)

Appliance or device

Power in W or kW

Power in watt (W)

Cellphone charger

Electric kettle

Television set

Light bulb (old type)

Energy saving light bulb

Computer

Electric iron

Teacher note: The values in the table are not exact, but the order of magnitude should be similar.

Appliance or device

Power in W or kW

Power in watt (W)

Cellphone charger

240 V and 150 mA

36 W

Electric kettle

2 kW

2000 W

Television set

60 W

60 W

Light bulb (old type)

100 W

100 W

Energy saving light bulb

15 W

15 W

Computer

230 V and 500 mA

115 W

Electric iron

1.4 kW

1400 W

Now arrange the appliances in the next table in terms of the power required. The list should be from small to large values of the power.

Appliance or device

Power in watt (W)

QUESTIONS:

What do you see in this table? Which two appliances have the lowest power requirements? What do these appliances have in common?

Possibly the cellphone charger and energy saving bulb. They are small and only require a small amount of energy to work. The bulb is built specifically to use less energy.

Which two appliances have the highest power requirements? What do these appliances have in common?

Possibly the kettle and iron (or any other heating device): they are used to produce heat which uses a lot of electrical energy.

Saving electricity

Electricity is expensive so we should try and save electricity.

This is not the only reason to try save electricity. Remember when we spoke about the pollution given off by coal power stations? Why else do you think it is important to try save energy and reduce your power usage?

The burning of coal in power stations produces carbon dioxide, a greenhouse gas, which contributes to global warming. If enough people reduce electricity usage in their homes, this will reduce the demand on coal power stations, meaning they have to burn less coal, which will in turn have less of an environmental impact.

There are many different ways to save electricity, from small actions, to larger actions, such as using renewable energy resources. We will discuss this a bit later in the chapter.

How can you prevent wastage of electricity in your home? Name four possible ways.

Use energy saving light bulbs, install a solar water heater, switch off all electrical devices that are not in use, and use as little hot water as possible.

Illegal connections

We discussed a world without electricity and we all realised how dependent we are on this resource. It is illegal for anyone to use electricity that was generated by ESKOM without their permission. Some people make illegal connections because they don't want to pay for the electricity. They cut through the insulation in a power line and attach other cables to this line. They can then direct some electricity to their house or workplace. These connections are dangerous to people as they are often unsafe.

People who make illegal connections try to get electricity for free but the dangers are not worth it. It is not worth your life!

Look at this mess of illegal electrical connections. http://commons.wikimedia.org/wiki/File:Alicia_Nijdam-rocinha.jpg

Electricity and safety

Accidents caused by electricity happen all the time. People often get hurt or even killed by electricity because they do not use it safely. Not only is it important to know how to use electricity safely, but also what to do if someone is hurt or shocked by electricity.

What types of emergencies can happen at home or at school with electricity?

Someone could get a shock on a plug or exposed wire, someone could put an electrical appliance in or near water and get a shock, there could be a power outage and when someone is trying to fix the problem, they could get shocked, etc

Find out about the emergency services in your area and write down their names and telephone numbers. Also write this information on a piece of paper and stick it to the wall next to your phone or in a central place in your home.

Consider inviting an electrician to talk about electricity and safety to the class.

Accidents with electricity can be avoided. We just need to be smart about working with electricity. Let's formulate some safety rules for working with electricity.

Safety rules when working with electricity!

This was done in Gr. 5, but it is a good idea to revise it again as electrical accidents often happen in the home and at school.

INSTRUCTIONS:

Look at each of the following pictures.

Each one shows someone doing something with electricity, and often the person is doing something dangerous!

Answer the questions about each of the pictures.

Electricity does not flow. Electric current flows. Be careful of introducing misconceptions here.

QUESTIONS:

The person in the illustration above is using a table knife to remove a coin that has fallen in the toaster before switching off the appliance. What are the dangers related to this act?

The person can get shocked as electricity can pass from the toaster, through the metal knife and through the person.

What safety rule can you formulate regarding this?

First turn the toaster off and unplug it and use a wooden or plastic knife.

Why is this an unsafe cable to use ? Circle the area that makes it unsafe.

What could be done to the cable to make it safe to use?

Replace the cord, or else wrap insulation tape around the broken cord. However, this will not prevent a short if the wires inside also have perished insulation. It is best to replace the cord.

What safety rule can you formulate regarding this?

Never use an appliance that has a broken cord or has some of the metal wire showing through the cord casing.

Why is it dangerous to pull the boy from the electric wire?

Electric current can flow from one person to the next, so you will also get shocked.

What can the helper do to save the boy without being shocked by the electricity?

Use a non plastic/non metal object to separate them from the electrical source.

What safety rule can you formulate regarding this?

NEVER try to pull someone who is being shocked away from the appliance.

Why is this not a safe place to play?

High voltage fences can shock you even if you stand near them without actually touching them, or you might accidentally bump against the fence.

What safety rule can you formulate regarding this?

Never play near to or on electric fences or power lines.

Why is this connection dangerous?

Too much electric current flowing to one plug is dangerous. One multi-plug adapter is safe, but do not put adapters into each other. Rather use 2 different plug points.

Teacher's note: The real danger is that overloading the plug causes heating of the circuit which can result in fire.

What safety rule can you formulate regarding this?

Never put too many appliances into one socket.

Why is it dangerous for the children to play outside during the lightning storm?

If this powerful natural electricity strikes close to you, it will try to get to the ground through you. Our bodies are good conductors of electricity.

Why should no one play under a tree when it is storming?

The lightning is attracted to high points such as a tree and can shock the tree and also kill anyone underneath it.

Explain why it is not a good idea to be swimming when there is lightning in the sky?

Lightning could strike the water. Water with dissolved substances, such as salt or chlorine, is a good conductor of electricity and you can get shocked, and possibly die if you are swimming.

What safety rules can you formulate regarding lightning?

Do not play outside when there is thunder and lightning.

Why is the gardener unsafe when mowing the lawn in the rain? Give at least two reasons.

Water is able to conduct electricity, so you can get a shock if you are touching an appliance and water drips into the socket, cord or motor. Secondly, he is not wearing shoes which is dangerous as he could cut himself and the current can flow through him and into the Earth.

What safety rules can you formulate regarding using electrical appliances outside in the garden?

Never use electrical appliances outdoors in wet weather or if you are wet. Wear shoes when using electrical appliances.

Renewable ways to generate electricity

renewable energy resources

non-renewable energy resources

solar

hydroelectric

geothermal

electrical power

We have seen above that fossil fuels are non-renewable resources of energy.

What do you understand by the word `non-renewable'?

This means it cannot be renewed, reused. There is a finite supply which will be used up one day.

So, if we are using an energy resource which is non-renewable, then this will be a problem in the future when these resources run out. Are there other sources of energy?

Scientists and engineers are looking for ways to harness energy from renewable resources. A renewable resource is the opposite to a non-renewable resource. It will not run out and can be used over.

Renewable energy sources include natural phenomena such as sunlight, wind, tides and plant growth. The energy comes from natural processes that happen over and over.

Renewable energy (video) http://www.youtube.com/watch?v=oTyWeW5MEio

Why do you think natural phenomena such as sunlight and wind can be considered as renewable?

This is because the sunlight and the wind will not `run out'. They are not used up or depleted in our time line. They will always be present on Earth (at least for a time frame relevant to human existence - the sun might extinguish one day in the far future, but this is not relevant when thinking of a renewable resource).

This is another place to speak of orders of magnitude. These resources are available so long as the solar system lasts in its current form, roughly 3.5 billion years they say. So these are renewable because they will always be available to us as a species even if we last a few million years more (having only really been around about 150 000 years or so).

Examples of renewable energy resources are:

solar (energy from the sun),

wind,

ocean (tides and waves),

hydropower (waterfalls or fresh water dams),

biomass (energy from plants and other organic material), and

geothermal (energy from steam underneath the surface of the earth).

Sun, wind and water can be used as sources of energy. Solar panels can be fitted to houses but this source of renewable energy works best on sunny days, and is less effective on cloudy days. Wind energy can be collected with a windmill or wind-turbine which can be big and noisy. Hydroelectric power stations harness the energy in water stored in high dams. It is only possible in areas where there are high mountains and rivers.

Solar panels which convert the sunlight energy to produce electrical energy are also called photovoltaics. There are also solar water heaters, but this is a different system to solar panels. Solar heaters directly heat water.

Wind turbines use wind to generate electricity.

Wind energy (video) http://www.youtube.com/watch?v=F3bZzOyMhKI&feature=player_embedded

A water wheel uses the flow of water to push the wheel around which can then do work.

The first windmills were developed in Persia in about 600 B.C. But, the first windmill to produce electricity was in Denmark in 1890.

As the water flows through this large hydroelectric power station, from the higher dam to the lower dam, electricity is made.

Solar panels

South Africa also has large reserves of uranium which are used in the Koeberg nuclear power station.

Renewable versus non-renewable energy

Learning how to debate is an important skill. After doing this activity, you could practise debating skills in the class by getting two groups to discuss opposing sides of the story. Each group must understand that they have to justify an argument for each side of the debate.

What are the advantages and disadvantages of renewable and non-renewable sources? There is a lot of debate around the use of renewable and non-renewable sources for energy. Let's join this debate!

INSTRUCTIONS:

Work in groups of four.

Discuss whether your house uses renewable or non-renewable sources of energy.

Does anyone in the group have solar panels at home?

Think about the advantages and disadvantages of renewable and non-renewable sources. You can use the Internet or other information sources to check for more ideas here.

Write some of your answers in the spaces below.

Report back to the class and see what others think about this debate.

Advantages

Disadvantages

Renewable

Non-renewable

How hydroelectricity works (video) http://www.youtube.com/watch?v=rnPEtwQtmGQ

If time permits, learners can do a mini research project on one of the renewable energy resources and present a poster in which they answer questions such as, `How is this renewable energy resource harvested and used to produce electricity?', `Is this resource used in South Africa?', etc. These can be stuck up as posters in the classroom for others in the class to read and learn from.

Most of our electricity comes from fossil fuels such as coal, oil and natural gas.

Fossil fuels are the remains of dead plants and animals from millions of years ago.

The energy in fossil fuels originally comes from the Sun which was captured by the plants that lived millions of years ago.

Electricity is expensive due to the infrastructure required to produce and deliver it.

Fossil fuels are non-renewable meaning they will run out.

We should try to be energy-efficient and not waste electrical energy.

Illegal connections pose a huge threat to people as they can be unsafe.

There are other resources which are renewable and can be used to generate electricity, such as wind power, solar power and hydropower.

Look at the flow diagram below. Describe what it is showing using what you have learnt in this chapter.

The Sun produces energy which plants capture and use to make food through the process of photosynthesis. Animals eat the plants. When these prehistoric plants and animals died millions of years ago, their remains were turned into fossil fuels (such as coal, oil and natural gas) over a long time. This was due to being covered in layers of sediment of mud and water which over time turned into rock and exerted a great pressure and heat on the remains. Today, these fossil fuels are mined and collected from inside the Earth's crust. Oil is processed to make petrol and diesel and the energy from the fossil fuels is used, for example in cars, where it is burnt and the energy released powers the cars.

Why are fossil fuels considered non-renewable resources?

This is because there is a limited supply of fossil fuels which will run out one day as we are using fossil fuels faster than they are made (which takes millions of years). They cannot be reused.

Write a paragraph in which you explain why you think humans should investigate alternative energy sources, such as renewable energy sources and how this might help the Earth.

Learner dependent answer, but assess whether learner has the ability to present an argument and justify their reasoning. One of the reasons which learners could present includes the fact that our reliance on non-renewable energy resources is not sustainable and poses a problem for the future if they run out. Furthermore, burning fossil fuels has a severe environmental impact as the carbon dioxide released contributes to greenhouse gases and global warming.

What type of electrical appliances in our homes use the most energy in a specific time?

This depends on the activity and usage, but the most energy will probably be used by heating devices such as a geyser or heater.

Imagine that you are writing an article for your local newspaper on how to save electricity in your homes. Use your imagination to write your article telling people how to save electricity. Use the space below. Give your article a catchy heading.

Assess learner's ability to write creatively about a science related topic. They are required to use the knowledge they have learnt in this chapter to write something creative. Tips to save electricity could be turning off lights when not in the room, using energy saving lights, reducing shower time to use less hot water, turning off the geyser during the day, using a gas stove instead of electrical stove, and bigger actions such as installing solar power, etc.

How do you think saving electricity will reduce the demand on ESKOM's power stations?

The more electricity you use, the more coal needs to be burned at the power stations to produce electricity. Saving electricity means that you use less electricity so there is less demand on the power stations.

What is an illegal electrical connection? How do you think the local government could stop or reduce the amount of illegal connections?

An illegal connection is when someone accesses electricity by cutting a power line and attaching another line and then not paying for it. The local government could try stop this by firstly trying to supply the poorer areas with appropriate electricity access points, going around and checking that there are not any dangerous connections, raising awareness about the dangers of illegal connections through advertising boards, on radio, in the newspaper, etc. Assess any other viable answers that the learner may come up with.

The solar system

How can we tell the difference between a star and a planet?

What are asteroids?

What is a moon? Does the Moon produce its own light?

Can we see the Moon during the day?

Do you remember that in Gr. 4 we looked at Space and the objects found in Space? Last year, in Gr. 5 we mostly looked at Earth and the features of Earth. Now we are going to explore Space a bit more! Before carrying on, let's refresh our memories on some of the things about Space from Gr. 4.

Wordsearch about Space.

INSTRUCTIONS:

Find the following words in the wordsearch.

Draw a circle around each word.

When you find the word, discuss with your partner what you remember about this word from Gr. 4.

space

gravity

astronomy

orbit

rotate

moon

axis

galaxy

sunrise

sunset

star

The birth of our solar system http://www.youtube.com/watch?v=B1AXbpYndGc

Teacher guide answer:

The Sun, planets and asteroids

Do you remember what a solar system is? Our solar system is made up of the Sun and the planets. Let's take a look!

What is the Sun?

The Sun glows so fiercely that it is not safe to look straight at it, even though it is so far away. The Sun is a ball of gases.

The temperature at the centre of the Sun is about 15 000 000 degrees Celsius! The surface is about 5 500 degrees Celsius. That is extremely hot! Can you see the explosion from the surface of the Sun in the picture?!

asteroid

furnace

core

wander

object

observatory

record

astronomer

gravity

Can you see the big burst of gas from the Sun in the bottom left?

Comparing the sizes of planets and the Sun http://sciencenetlinks.com/interactives/messenger/psc/PlanetSize.html

The Sun is a star, because it produces its own energy. The Sun appears bigger and brighter because it is much nearer to Earth than the other stars.

The Sun is about 150 million kilometres from Earth and the next nearest star to us after the Sun is over 40 million million kilometres away.

The Sun is about 420 times bigger than the Earth and about 1700 times bigger than the Moon! The Sun is much further away than the Moon from the Earth. The Sun produces light and heat. The heat warms the surface of the Earth.

Study the image of the Sun, and then answer the questions that follow in the activity below.

This image shows the different layers of the Sun.

The core of the Sun

INSTRUCTIONS:

Look at the picture of the Sun showing the different layers inside.

Answer the questions.

QUESTIONS:

Which is the hottest part of the Sun?

The hottest part of the Sun is the core, that is, the middle, white part.

The Sun's energy comes from gases being squeezed together until hydrogen turns into helium. Where do you think the gases are squeezed together the hardest?

in the core

What are the dark spots on the surface of the Sun called?

sunspots

When the Sun has changed all its hydrogen into helium and other substances, it will begin to die. But we need not worry, because that will happen 10 000 million years from now.

Planets

The following pages contain a lot of text and not much in the way of activities and writing. This is intended to be told as an interesting story to your learners. Read through this together. Get learners to read different parts at different times. As you are going through it, ask the class different questions, such as "Do you know the names of any constellations?", "Can you remember the names of all 8 planets?", "Do you know the names of any other Greek philosophers?" (E.g. Socrates, Plato, Aristotle). This can also be used as revision to remind learners about what they learnt in Gr. 4 about the solar system.

Long, long ago, people watched the stars at night. Shepherds looking after sheep and cattle would lie down and look at the night sky. People in hot regions like Mesopotamia (now Iraq) slept on the roofs of their houses. They had plenty of time to look at the stars. They knew the patterns of stars in the sky and how the stars moved across the sky during the night. The patterns were fixed (they did not change). For example, you can find a pattern like the Southern Cross if you look up towards the South. You can see it in the first photo below. The second photo with white lines helps you to see the Cross. It always looks the same because the stars are always the same distance apart.

This pattern of stars is the Southern Cross. The pattern does not change.

The white lines are not really in the sky, they just show you how to view the Southern Cross.

Patterns of stars are called constellations. The next image shows some other famous constellations of stars which you can see in the night sky.

Some constellations of stars making up patterns in the sky

People noticed that some bright objects did not behave like the others. These objects are close to a star one night and then the next night, at the same time, the object has moved away from the star. Night after night, these objects appear in new positions among the stars.

The Greeks of those times called these objects "the wanderers" because they were in a slightly different position each night. The Greek word for wanderer is "planetes" and so we get the English word "planet". A person who wanders is someone who walks around wherever he feels like going.

The Wanderers (movie) http://science.gsfc.nasa.gov/690/solarsystemtour.html

The planets were a science puzzle

People who study the stars are called astronomers. The planets were a puzzle for ancient astronomers. Why did they move differently to the stars? Were they just as far away as the stars? Why were they brighter at some times of the year than at other times?

You can see the planet Venus just after the Sun has set. Venus is usually very bright. At some times of the year, you have to look for Venus in the dark sky where the Sun will rise.

The ancient peoples gave names to the planets. For example, Mars was named after the god of war. One planet was so beautiful that they called it Venus after the goddess of love and beauty.

You can see Mars at some times of the year. Mars is orange-red, and at most times it looks smaller than Venus. It is not as easy to find as Venus is; sometimes you have to look late at night to see Mars rising in the east.

How astronomers solved the puzzle

Over hundreds of years, astronomers set up observatories in places like India, Egypt, Iraq, England and countries in Europe. An observatory is a building that has permanent measuring marks. These marks are always in the same position. The astronomers make notes of where stars and planets are compared to these fixed positions, and they note the dates and times.

A system is a set of parts that work together. Any change or movement in one part causes changes in the other parts.

Hypatia was an astronomer and mathematician at the University of Alexandria in Egypt. She lived about 1700 years ago. Can you see the globe next to her in this old drawing?

Over many years of careful observing, the astronomers kept records of where the planets moved. They used maths to predict where a planet would be on a future date. Then, on that date, they went to check if their prediction was correct. They became very good at measuring, doing maths and doing calculations with big numbers.

Ancient astronomers making observations

So they worked out that the planets are closer to us than the stars, and that the planets are moving around the Sun. Then they realised that Earth is a planet too, and it is moving around the Sun!

This idea upset some people who believed that the Earth was the centre of the universe and that everything moved around the Earth. Nowadays we know exactly where each planet in our solar system is at any time, and we can actually send spacecraft to the planets.

The Sun together with the planets moving around it is called the solar system. You will learn about that next.

The solar system (video) http://www.youtube.com/watch?v=z_RAEESmsrs

The solar system

The solar system consists of the Sun and all the planets that orbit around it. It also includes asteroids and the planets' moons.

In the first image, you can see a diagram of the solar system. In the second image in the next activity, you can see another diagram of the solar system. Both these diagrams try to show you what the solar system is like.

The birth of the planets http://www.youtube.com/watch?feature=endscreen&v=o-pLrbwOGzA&NR=1

The solar system consisting of the Sun and 8 planets

Pluto used to be classified as a planet. But not anymore.

In the solar system, each object's force of gravity pulls on all the other objects. Gravity is a force of attraction between objects. The Sun is the biggest and heaviest object in our solar system and so it exerts the greatest force of gravity on all the planets. This force of gravity makes all the planets move in circles around the Sun.

The names of the planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury is the planet closest to the Sun and Neptune is the planet furthest from the Sun.

Why isn't Pluto a planet anymore? http://www.youtube.com/watch?feature=endscreen&v=FqX2YdnwtRc&NR=1

Earth is the third-closest planet to the Sun. Find Earth in the picture.

Could the planets really be as close to the Sun as the picture shows? Give some reasons for your answer.

No, they are not really this close. Reason 1: A person on Earth would see the Sun filling half the sky, but we know that the real Sun looks quite small in the sky. Reason 2: All the water on Earth would have evaporated and all living things would burn up.

Looking at the solar system from far away in Space

INSTRUCTIONS:

Imagine you are in a spacecraft very far from the Earth. You can see the planets all moving around the Sun in orbits, like in the picture. The white lines in the picture show the path that each planet follows when orbiting the Sun. These orbits (white lines) are not actually visible.

Look at the picture and answer the questions.

QUESTIONS:

Which planet is the closest to the Sun?

Mercury

Is Venus or Earth closer to the Sun?

Venus. The learners can see this if they follow the orbit of Venus and Earth with a pencil. Tell the learners to compare this diagram with the previous one and use the information they have already got above, about the order of the planets. This teaches learners that textbooks provide information in different places because they cannot provide all information in the same place.

Write the names of the planets in order, beginning from the one that is closest to the Sun.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Mercury is the planet closest to the Sun and Neptune is the planet furthest from the Sun.

Which planet do you think is the coldest, and why?

Neptune. It is the furthest away from the Sun.

Why do the planets all keep on moving in orbits around the Sun?

The force of gravity between the Sun and each planet keeps them moving in their orbits. The Sun is so big and heavy that it can exert a force of gravity that pulls even the furthest planet, Neptune, into its orbit.

The word "solar" comes from a Latin word "sol", which means "sun".

Let's now use our bodies to create a model of how the planets move around the Sun!

Make a model of two planets moving around the Sun

This is a demonstration, using two learners at a time. One learner must run with the ball to get it moving in a circle. You need plenty of room; at least a clear 10-metre-diameter circle. The long string helps to give learners the correct idea that the Earth's orbit is at a very great radius from the Sun. Plan this to happen at the start or end of a period, because the learners take time to move outside. This activity was also included in the Gr. 4 workbook to show revolution of the planets around the Sun. In Gr. 6, it is also important for learners to understand that not only do planets revolve around the Sun, but they also rotate on their axis. After doing this activity, also get one learner to stand in the centre as the Sun and hold several pieces of string, or you the teacher can do this. Several learners then hold the ends of the strings and spread out and walk around the teacher/learner in the middle. They are now revolving. As they are revolving, ask learners to now also spin as they are revolving. Explain that they are now also rotating as planets rotate on their axis at the same time that they are revolving around the Sun.

MATERIALS:

strong string about 5 metres long

another strong string about 3 metres long

two balls in plastic bags

eight thick rubber bands

a small chair or a box like a plastic milk crate

INSTRUCTIONS (Part One):

Tie the four elastic bands onto the handles of the plastic bag. Then tie the string onto the four elastic bands. Put one ball inside the bag.

You are going to do as you see in the next picture.

Someone must run with the ball in the bag to help you get it going.

Then swing the ball around as fast as you can, on the end of the string.

The rest of the class must watch the plastic bag carefully to see whether the rubber bands stretch.

You see the learner in the picture swinging the ball around himself. The learner represents the Sun and the ball represents the Earth.

Take turns to swing the ball; feel how hard you need to pull on the ball to keep it going around.

The people who are watching will see the rubber bands stretch. This means that the ball is pulling on the string, and the string is pulling on the ball.

QUESTIONS:

What does the learner who is swinging the ball represent? What does the ball represent?

The learner is the Sun and the ball is the Earth.

What do you feel is happening to the elastic as you swing the ball?

You will feel the string pulling on your hand.

If the ball in its bag could feel, what would it feel?

The ball will feel a force pulling on it equal to what the hand feels.

If the string breaks, in what direction will the ball carry on travelling? Draw an arrow on the picture to show the direction the ball would carry on moving in.

Give learners time to think about this, and commit themselves to an answer. The answer is that the ball will continue travelling in the direction it's going at the moment the string breaks. Learners can test this answer by letting the string go.

The ball represents the Earth. The learner swings it quite fast, but how long does the Earth really need to go once around the Sun?

It takes the Earth one year to orbit the Sun.

INSTRUCTIONS (Part Two):

This part is more difficult and it needs some practice. You are still making a model of planets moving around the Sun.

Use the 3-metre string and tie it onto a bag and ball as you did before.

In the picture you see one learner standing on a stool and swinging another netball in a bag.

The first learner now has to walk around the stool to keep his ball moving.

This might take some time to get it right!

Two learners must now swing balls at the same time. This is quite tricky!

QUESTIONS:

Which part of this model represents the Sun?

The two learners together represent the Sun.

Which part of the model represents planet Earth?

The first ball on the 5-metre string represents Earth.

Which part represents planet Venus?

The second ball on the 3-metre string represents Venus.

In this model, when Earth revolves around once, how long a period of time does that represent?

It takes one year.

The planet Earth orbits around the Sun in 365.25 days and we call that one year. As Earth moves to new positions around the Sun, we have four seasons: summer, autumn, winter and spring, and then summer comes again.

Now in Space, the Earth keeps on going around the Sun at more than 100 000 kilometres every hour. However, there is no string pulling on the Earth, so what keeps it moving?

The force of gravity pulls the Sun and the Earth towards each other.

The planet Venus orbits around the Sun in 224.7 days. Those are 224.7 Earth days.

There is no string in Space between Earth and the Sun! The Earth would move away, but the Sun "traps" the Earth with its much greater force of gravity. The Sun pulls on the Earth and the Earth pulls on the Sun with the force of gravity. The pull is so strong that it works at a distance of 150 million kilometres! Like the string, force of gravity keeps the Earth moving in its orbit around the Sun, year after year.

It does the same for the other planets too. The force of gravity pulls the planet Neptune into its orbit even though Neptune is 30 times further away from the Sun than Earth is.

In the model in the previous activity, what does the string represent?

The string represents the force of gravity between the Sun and a planet.

We visit the eight planets

The four inner planets are rocky.

Look at the picture below of the solar system again. The 4 planets closest to the Sun are called the inner planets of the solar system. They all are made of rock; some of them have a thin layer of gas on the outside. Earth has a very thin layer of water and soil too.

These are the 4 inner rocky planets. This shows their sizes compared to each other. Can you name them?

The next image shows us what the core of each of the rocky planets looks like. The core is the inner part of the planet and it is made up of different layers.

The core of each of the four inner rocky planets of our solar system.

Give the names of the four inner, rocky planets by looking at the pictures above.

The learners must work it out from the figure. The skill is interpreting the picture below and the text above. Mercury, Venus, Earth, Mars

Name the 3 layers of the rocky planets. Hint: They are each given a different colour in the image above.

crust, mantle, core

The four outer planets are gas giants.

These planets are very far from the Sun. They don't have a hard surface that a spacecraft can land on. Instead, they are giant balls of very cold gases. Astronomers think that these planets have hot, solid cores, deep down inside them.

This diagram shows the different sizes of the planets. Can you see how much bigger the 4 outer gas giants are?!

This next image shows us what the inside of the gas giants is like. There are also different layers of gases.

Introduction to the planets (video) http://www.youtube.com/watch?v=N2EU96xqEk4

The four gas giants, showing the gases which make up these planets

Give the names of the four outer, gas planets by looking at the pictures above.

The learners must work it out from the picture. Jupiter, Saturn, Uranus and Neptune

Give the name of one of the gases that make up the gas planets.

The gas planets are made up of hydrogen, helium or methane.

Let's now take a closer look at each of the planets.

Mercury is closest to the Sun, and the smallest planet. It has no atmosphere and its grey surface is marked with thousands of craters. A crater is the mark that we see where a rock has crashed onto a planet or a moon.

Can you see all the craters on the surface of Mercury?!

Venus alternates every 584 days between being an "Evening Star" and a "Morning Star", in other words shining brightest just after sunset, or just before sunrise.

Venus is second closest to the Sun. It is almost the same size as Earth. To us, it looks white and it shines brightly in the evening or morning.

Venus shines brightly like that because it is covered in a thick cloud of gas. It would be horrible to breathe the atmosphere on Venus, because the gas is mostly carbon dioxide and sulphuric acid! The atmosphere absorbs lots of heat from the Sun and does not cool down at night. Venus is the hottest planet in our solar system.

The temperature is about 450°C on the surface of Venus!

This beautiful image of Venus was created from a whole lot of photographs taken by NASA over 10 years, put together to make a single image.

Video on Venus http://www.youtube.com/watch?v=Hg_NzWbsvxE

Venus rising next to the Moon

At what temperature does water boil?

100 degrees Celsius

Zinc melts at about 420°C, so what would zinc look like on the surface of Venus?

It would be a liquid.

Then we reach Earth - the blue planet, our home in Space. You know a lot about Earth already. Earth has its Moon that we know well. The Moon moves in its orbit around the Earth.

This image is from a satellite tracking a hurricane moving over Earth's surface. Can you see the hurricane? It appears as the white swirl of cloud on the picture.

The wonders of Earth (video) http://www.youtube.com/watch?v=thuViaxRd_w&feature=fvwrel

Next furthest out is Mars, the red planet. We know quite a lot about Mars. Many spacecraft have been sent to Mars to take photographs and some spacecraft even landed to take samples of the soil.

We cover some extra information on Mars because the learners need to search for information when they carry out a case study of the Mars rover in Unit 4.

Mars needs almost two Earth years to complete one orbit around the Sun, so if you lived on Mars you would have to wait a very long time for your birthday. Mars spins like the Earth, and a day on Mars is almost the same length as a day on Earth. A day on Mars is called a sol.

Can you see the long, darker mark across the surface of Mars? This is a deep valley.

Rock around the World http://ratw.asu.edu/

This planet is further from the Sun than Earth, and for this reason it is very cold. It has a thin atmosphere but this atmosphere is mostly carbon dioxide gas. Humans cannot breathe that atmosphere.

The surface is mostly sand and rocks. The sand is full of iron oxide, which is the same substance as red-orange rust. From Earth we see Mars as a small red-orange dot in the sky, because of the colour of the soil.

This is a very recent photograph of the surface of Mars, taken in 2012 by the rover called Curiosity. Can you see all the rocks?

A video from NASA about the surface of Mars http://www.nasaimages.org/luna/servlet/detail/NVA2~27~27~65049~127816

There are some very big valleys on Mars. Valleys are caused by erosion when water flows downhill, so we can make an inference that there was a lot of water on the planet long ago. If there was water, perhaps there were living things on Mars too. But we cannot be sure. Scientists have sent another spacecraft to look carefully at the rocks and sand. The spacecraft is called Curiosity and it will try to find signs of living things in the ground.

This is a closer view of the valley you saw on the surface of Mars. On Earth, valleys like this are caused by water. Did Mars have water long ago?

NASA video on Valles Marineris http://www.nasaimages.org/luna/servlet/detail/NVA2~20~20~54397~125187:NASA-KSNN---Mars-Records

Mars is smaller than Earth and if you went there, your weight would be only about a third (⅓) of your weight on Earth.

If your mass is 45 kg on Earth, you weigh 450 newtons (N). If you went to Mars, what would you weigh?

450 newtons ÷ 3 = 150 N. So the answer is 150 N. Show this calculation on the board and explain how to do it.

In fact, your weight on Mars would be 37,7% of your weight on Earth. We have rounded the number to simplify the calculation. If learners query this then you can show them the following calculations: 450 newtons \(\times\)\(\dfrac{\text{37,7}}{\text{100}}\) = 169.65 newtons

Would you feel heavier or lighter on Mars?

You would feel much lighter on Mars!

Now we have to go very far from the Sun, 5 times further than Earth is from the Sun. We begin to see the gas giants, which are the four outer planets. These gas giants have no solid surface we could land on. They are huge balls of gas and if we came close we would fly through clouds of cold gases.

Before we can get to Jupiter, we have to pass safely through the asteroid belt. You can read about the asteroid belt further down this page.

Jupiter is the first gas giant we come to, and it is the biggest of all the planets. From Earth we see it shining white but close up, its colour is light pink-brown. It is bigger than all the other planets put together.

Jupiter, showing the swirling light pink and brown colours on the surface.

Jupiter is a huge ball of gases such as hydrogen, with clouds of ammonia. Winds blow from east to west on Jupiter's surface, and they blow at the speed of jet planes. The surface is very cold, and some of the gases are so cold that they have become liquid or solid.

Deep inside, Jupiter may have a very hot core of rock. Jupiter has four big moons, and sixty smaller ones.

A video on Jupiter http://www.youtube.com/watch?v=s56pxa9lpvo&feature=endscreen&NR=1

You will read about Galileo in Chapter 5. He was the first person to see the moons of Jupiter.

If we now go even further into Space, to double the distance we went to reach Jupiter, we reach the planet Saturn. Saturn is almost as big as Jupiter but it has a light yellow colour. It is mostly gas and it has rings of rock spread out and spinning around it. Saturn has about 62 moons.

The above image is an artist's drawing of the Cassini spacecraft approaching the planet Saturn and its magnificent rings.

Saturn isn't the only planet with rings. The other gas giants, Jupiter, Uranus and Neptune also have rings - they are just less obvious.

Then we get Uranus, a smooth blue-green ball of gas, with almost no marks and shapes on it that we can see. It has more than 25 moons.

The blue globe of Uranus shown here with 5 of its major moons.

Now we are more than 30 times further from the Sun than Earth is, and we see the last planet, Neptune. Neptune is also a ball of gas and looks like Uranus. It has about 12 moons, and possibly more. Neptune has a very 'stormy' surface. Images of the planet often show huge storms and winds.

Look at this close-up of the surface of Neptune. Can you see the stormy surface? These are the darker blue and white spots.

The following activity tests comprehension skills. It is a good idea to read through the text together and then allow learners to go back and read it by themselves when looking for the answers.

Comprehension on the 8 planets of our solar system.

INSTRUCTIONS:

We have read a lot about the planets in our solar system.

Use all the information and images in the previous pages to answer the following questions.

QUESTIONS:

Name all the planets in order starting from the one closest to the Sun.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune, Uranus

What are the 4 inner planets known as?

The inner, rocky planets

What are the 4 outer planets known as?

The 4 outer planets are known as the gas giants.

Which planet is the hottest?

Venus is the hottest planet.

On which planet do scientists think there might have been water long ago? Why?

On Mars, because there are valleys on the surface which look like they have been made by water erosion.

Which planet has a "stormy" surface?

Neptune has a stormy surface.

Venus also has an atmosphere like Earth, but we would not be able to breathe there. What gases make up the atmosphere on Venus?

carbon dioxide and sulphuric acid

Below is an image showing the temperatures of the planets. Mercury is the closest to the Sun, but Venus is actually hotter than Mercury. This is because of the dense atmosphere of Venus which acts like a greenhouse and traps the Sun's energy in the atmosphere. Use the image to give the temperatures of Earth, Jupiter and Neptune.

The temperatures of the planets

Earth: 15 C

Jupiter: -110 C

Neptune: -200 C

Which is the biggest planet in our solar system? What colour is it?

Jupiter, pink-brown

Which planet is blue-green in colour?

Uranus

Saturn has rings around it. What are these rings made of?

Draw a picture of Saturn in the space below.

Asteroids

What a strange word - asteroid! Have you heard this word before? Maybe when we mentioned the asteroid belt?

The asteroids are lumps of rock from planets that broke up long ago. Some of the lumps are bigger than a school building and some are only as big as small stones. They orbit around the Sun and so they are travelling very fast. Some of them are travelling as fast as 25 kilometres every second. That is much faster than a bullet.

This is a photo of the asteroids Ida and Gaspra. Ida is the bigger one and is 30km long.

Many scientists believe that an asteroid hit Earth and caused the extinction of the dinosaurs around 65 million years ago.

The asteroids have gathered together in a ring in the solar system. This ring is called the asteroid belt.

Where is the asteroid belt?

INSTRUCTIONS:

Find the asteroid belt in the picture below.

Write out the whole sentence below and complete it.

Use some of the words from the box.

Word box

Mars

Jupiter

Venus

pieces of rock

in orbit

the Sun

Asteroids are _____ that move _____ around the Sun. The asteroid belt is in Space between the orbit of _____ and the orbit of _____.

Pieces of rock, in orbit, Mars, Jupiter

In 1973, Pioneer 10 was the first spacecraft to travel to Jupiter. To get there, Pioneer 10 had to go through the asteroid belt. Do you remember how fast asteroids are moving? If an asteroid had hit Pioneer 10, the spacecraft would have been destroyed and smashed to pieces. However, Space is a very big place and the asteroids are usually far apart. Pioneer 10 got through safely and went on to take the first close-up photos of Jupiter.

An artist's painting of the Pioneer 10 spacecraft near Jupiter after it was the first to cross the asteroid belt.

Moons

You know from the section on planets that other planets have moons.

Earth's Moon

Let's begin with Earth's Moon. You learnt about Earth's Moon in Gr. 4. So what do we already know about Earth's Moon?

reflect

crater

volcanoes

lava

compare

measure

record

surface

Let's revise what we learnt in Gr. 4 about the Moon.

QUESTIONS:

Does the Moon make its own light? Explain how the Moon gives us light at night.

The Moon does not have energy like the stars to make its own light; the Moon is like a white wall that reflects light from the Sun, and the Earth gets some of that light.

Can we see the Moon during the day?

Yes, on some days. But if they are unsure, don't give them the answer. Let the learners debate this or vote on it, and then agree to go and observe. They might have to look every day, for up to two weeks, before they see it.

Does the full Moon look bigger when it rises at supper-time, and then smaller when it is high in the sky?

If they disagree on this, tell them that they can do an investigation - see below.

Why does the Moon sometimes look like a letter D or a letter C?

We see only the part that the Sun is shining on. They learnt this in Gr. 4 workbook.

Is it easier to see the stars when the Moon is full or when it is not full?

It is easier to see the stars when the Moon is not full.

Why do we sometimes see the new Moon looking like this, in the next photo. The Sun is almost behind the Moon, so where is the light coming from?

The light on the Moon is coming from the Earth; the Earth is reflecting the Sun's light.

Only one side of the Moon in this photo has light on it. Where is this light coming from?

Compare the Moon with the Earth

INSTRUCTIONS:

Work with a partner or in a small group.

Look carefully at the picture and answer the questions.

The Moon and the Earth - showing the difference in size

QUESTIONS:

List all the differences you can see between the Earth and Moon.

The Earth is bigger than the Moon. The Moon has craters, but few craters are still visible on Earth (due to wind and water erosion).

The Earth has water in seas, the Moon has none; Earth has areas where green things are growing - there are none on the Moon; clouds on Earth, but none on the Moon.

List some differences that you know about, even though you can't see them in the photos.

The Earth has plants and animals, but there aren't any on the Moon. Earth has an atmosphere, but the Moon does not. The Moon gets very hot and then very cold; Earth's temperatures stay in a range where things can survive. You are heavier on the Earth than you are on the Moon.

Many people say that the full Moon looks bigger when it rises just after sunset, and then looks smaller late at night. Is this true? Let's do an investigation to find out.

The following investigation needs to be carried out on a night when the Moon is full. Come back to it at a later time in the month if you have to wait awhile and carry on with the rest of the content in the meantime.

Does the Moon look bigger when it rises than when it is high in the sky?

AIM (What you want to find out):

HYPOTHESIS (What you think will happen):

APPARATUS:

You need to know the date when the Moon will be full.

a piece of wire shaped like a V (you can make this from a paper clip)

a ruler

METHOD:

Just after sunset on the right date, look for the rising Moon.

When you see it coming up behind some trees or buildings, hold out your width-measure as you see in the picture below.

Hold your width-measure at arm's length.

Bend the wires until the points (the tips) of the wire touch the sides of the Moon. You must keep your arm straight while you measure the Moon. Can you think of the reason why?

The arm is part of the measuring instrument, because it is an unchanging length! If the child moves her hand closer to her face, the V-shaped measure will give smaller measurements.

Go inside and use a ruler to measure how far apart the tips of the width-measure are.

Record your measurement in millimetres.

Go outside again about two hours later and measure the width of the Moon a second time. Remember to keep your arm straight while you measure.

Come inside and use the ruler again. Measure the distance between the tips on your ruler again.

Record your measurement in millimetres.

RESULTS AND OBSERVATIONS:

Width of the Moon when it was touching the trees: _____ mm

Width of the Moon when it was high in the sky: _____ mm

How could you have done this investigation better?

Most of them will find that the measurements are the same. Some learners will have made mistakes and will say that the high Moon was smaller, so you can ask for a show of hands - "who found that the measurements were the same at 6:00 and 8:00 p.m.?" Now in science, ideas cannot be tested by majority vote. In science, just one careful investigation can undo a majority opinion. If other people can investigate the idea and get that same measurement, then an idea can be changed or confirmed. You can ask the class to go and repeat the investigation tonight. The Moon will still be full, but will rise about 50 minutes later.

CONCLUSION (What you learnt):

Write down a conclusion about what you learnt from this investigation.

They should learn that in science we want to test ideas to find out whether they are true or not. If we measure things, we can sometimes be more certain of the truth.

The Moon has a pale grey surface with dark grey marks on it. Nobody knew what the surface was like until spacecraft landed on the Moon. The first astronauts to walk on the Moon stepped into fine, powdery dust. They collected rock samples (small pieces) to bring back to Earth.

The surface of the Moon is covered with holes called craters. These craters are made by space rocks that hit the Moon. These rocks may be as small as grains of sand or as big as a house. They travel so fast that they explode when they hit the Moon, and they make a round hole.

The footprints from the astronauts who first walked on the Moon are still there! There is no wind on the Moon to blow them away.

The footprint of the first person to ever stand on the Moon

The surface of the Moon - can you see all the craters?

The light-coloured areas on the Moon are mountains, and the darker areas are plains. Some of these plains were made by huge space rocks that made craters 300 km wide. Other plains were made by volcanoes on the Moon a long time ago. Lava* flowed out from those volcanoes. Nowadays the Moon has no volcanoes.

The Moon has no air so there is no wind to blow the dust. The Moon has no water, so there is no rain to wash away sand and cause erosion. That is the reason why we see the craters on the Moon so clearly.

A spacecraft a few years ago found signs of water frozen under the south pole of the Moon. Scientists are not sure how the water got there.

Moons of other planets

Other planets have moons, too. Below is an image showing some of the moons in our solar system. Not all of them are shown here. They have been scaled to be the correct size compared to Earth and our Moon.

Mars has two moons, and astronomers called them Deimos and Phobos. Phobos has deep craters showing that it has also been hit by fast-moving rocks. Can you see how small these moons are compared to our Moon?

On the other hand, Jupiter has 66 moons which we have identified, and each time humans send another space probe to Jupiter, more moons are being discovered! Only Jupiter's 4 biggest moons are shown below.

Some of the moons in our solar system

Quick tour of planets and their moons http://www.youtube.com/watch?v=9ETwG8X54MA&feature=related

Moons in our solar system

INSTRUCTIONS:

Look at the picture above of the moons in our solar system.

Answer the questions below.

QUESTIONS:

How many moons does Earth have?

Earth has one moon.

What are the names of Mars' two moons.

Phobos and Deimos

Give the name of one of Jupiter's moons.

Io, Europa, Ganymede or Callisto

Pluto is not actually a planet anymore, but it has been classified as a dwarf planet. Pluto also has 3 moons. How many of Pluto's moons are shown in the picture?

Only one of Pluto's moons are shown.

There are two planets which are not listed here as they do not have any moons. Which two planets are these?

Mercury and Venus

What is the name of Saturn's biggest moon?

Titan

The Sun is at the centre of our solar system.

Planets move in orbits around the Sun.

Planets cannot produce their own light; they reflect light from the Sun.

Asteroids are rocks that move in orbit around the Sun. They are very much smaller than planets.

Most of the planets have moons. A Moon is a body which orbits around a planet.

The table below is a comparison of planets and stars. Choose sentences from the box below and write them under the heading "planets". Match your sentences about planets to the sentences about stars.

Stars

Planets

Stars are very hot balls of gas that give out light and heat.

Planets do not make their own light; they reflect the light from the Sun.

We can see thousands of millions of stars with a telescope.

We can see only 7 other planets in our solar system.

Stars are very, very far away from us.

Planets are not as far away as stars.

Stars do not orbit around our Sun.

Planets orbit around our Sun.

The stars seem to stay the same distance apart always.

Planets change their positions each night, compared to the positions of the stars.

Sentences to select from:

Planets do not make their own light; they reflect the light from the Sun.

We can see only 7 other planets in our solar system.

Planets change their positions each night, compared to the positions of the stars.

Planets are not as far away as stars.

Planets orbit around our Sun.

If you wanted to find Venus, where would you look? At what time would you look?

Venus can be seen in the west, just after sunset. Sometimes it is visible in the morning, so then you would look in the East at sunrise.

People call Venus the evening or morning star. Explain why Venus is not a star.

Venus appears in a slightly different position each evening at 7:00 p.m, or each morning at sunrise.

Here are two sentences about the solar system. The 2 sentences have been broken and the parts are mixed up. Work with a partner to sort out the parts. Then write out both sentences in your book.

The solar system is

the Sun.

The Sun and all the planets

a set of parts that

pull on each other.

the planets move around

pull on each other as

The solar system is a set of parts that pull on each other. The Sun and all the planets pull on each other as the planets move around the Sun.

What made the craters on the surface of the Moon?

Rocks that travel through Space, called meteoroids. They crash into the Moon at very high speeds.

The surface of the Moon has many craters but the surface of the Earth has very few craters. Explain why that is so.

(a) The Moon has no atmosphere to protect it. Earth has an atmosphere so most rocks from space burn up before they reach the ground. (b) Earth has been hit by meteoroids, as the Moon was, but erosion has worn down the craters so that we cannot see them clearly any more.

Neil Armstrong was the first man to put his foot on the Moon. His footprint is still there after 40 years. On Earth, a footprint does not last so long. Explain why it lasts so long on the Moon.

The Moon has no rain and no wind to remove the footprint.

The Earth is travelling through Space at 100 000 kilometres in every hour. How can we work that out? Here is information for you to use: The length of the Earth's path around the Sun is 942 million kilometres and it takes 365¼ days to go all the way around. Now you can work it out for yourself. Hint to help you: How many hours are there in one day?

This is a challenge for your learners. They will not be used to working with very big numbers. They will probably need calculators. However, they know what answer they should get.

Movements of the Earth and planets

If it is nighttime in South Africa, is it also nighttime in Brazil?

Do the other planets also take a year to revolve once around the Sun? Is their year the same length as our year on Earth?

Why do we get day and night?

What is the difference between revolution and rotation?

Rotation (Earth)

For a long time people believed that the Earth stood still and the Sun moved around the Earth. In this chapter we will find out what really happens. We'll start by thinking about day and night.

Day and night

During the day, it appears as though the Sun moves across the sky as it rises (comes up) in the morning and sets (goes down)in the evening.

rotate

spin

rotation

direction

East and West are two directions you must know. If you point at the Sun when it appears to rise in the morning, you are pointing in the direction of East. If you point at the place where the Sun sets, you are pointing direction of West. Have a look at the picture of Sophie. Sophie loves to get up early and watch the sunrise. She is standing with her arms stretched out, pointing in the directions East and West.

You can tell the direction from the rising and setting of the Sun.

Short video showing the Sun, Earth and Moon system http://www.youtube.com/watch?v=W47Wa7onrIQ

Find East and West

MATERIALS:

a place where you can stand in the early morning

INSTRUCTIONS:

Look at the picture of Sophie at sunrise and answer the questions.

QUESTIONS:

Which is Sophie's right hand? Show her right hand with your finger.

Why do we see a shadow of Sophie on the ground?

The Sun is casting the shadow as Sophie is blocking the light from the Sun which reaches that part of the ground.

In which direction is her shadow pointing?

West

If Sophie looks straight in front of her, in which direction is she looking?

North

Now find the direction of East in your classroom. You must point to the place where you see the Sun come up in the morning. In the classroom, stretch out your arms and point in the direction of East and West. Clean the floor and stick some insulating tape on the floor so that everyone can remember which direction is East and which direction is West.

Help your learners understand that East is not really a place. Wherever you are on Earth, you can point towards East and if you keep walking East you will see the sunrise in front of you every morning. This idea can be a little confusing because we do talk about places like Mpumalanga, the place where the Sun rises. But if you actually go to Mpumalanga's eastern border, then you see the Sun rise over Mozambique. In Mozambique, the Sun rises over the sea, and so on.

So the difference between the words "place" and "direction" is important. We see this if we ask the question "How far must I walk to reach the East?" The answer is "You can never reach it; the East will always be in front of you."

This becomes practically significant when we tell the learners that the Earth rotates towards the East. You cannot find a place on the globe that is marked "the East".

What does the word "direction" mean? You can walk in a direction towards a place. If the wind blows, you see leaves moving in the same direction as the wind. Remember, a direction is not a place that you can reach!

Introduce what it means to discuss something with someone else. You can also introduce the concept of debating, which is a more formal discussion where two opposing (opposite and different) views are put forward on a topic and each group argues their case. Allow learners a few minutes to discuss the following question with their partner. Then ask for some feedback on the answers.

Let's have a discussion. To discuss something is to talk about it and your ideas with someone else or a group of people. Turn to your classmate next to you and discuss the following question. Write your answer down, then write your partner's answer down.

Where does the Sun go at night? Why do we get day and night?

Your answer is:

Your partner's answer is:

NB: The Sun does not actually "go" anywhere at night! We may talk about the movement of the Sun across the sky in everyday language, but this is INCORRECT. The Sun does not move - the Earth rotates on its axis. In the rest of this section, make it clear to learners that the Sun may appear to move across the sky, but it is actually the Earth that is spinning which makes it look like the Sun moves.

In this next section we will find out these answers!

Does the Sun really move, or does the Earth move?

When you ride in a bus, you may see houses outside the bus. It looks as if the houses move past your window.

Why do the houses seem to move past your window? Are the houses really moving? Discuss this question.

Don't accept an answer "No, they are not moving"; ask why they seem to move. Learners must realise that the houses seem to move but it happens because the person in the bus is moving. We want learners to put this idea into words for themselves.

So it is really the person in the bus who is moving; it looks to the person as though the houses are moving, but they are not moving.

You saw how big the Sun is when we compare the Earth and the Sun. Go back to the beginning of this term's work to find the picture of the Sun and the Earth. That great big Sun does not move around the Earth.

The Earth is turning around and that is why we see the Sun move past us. We are like a person in a bus. They are in the bus and they are moving past the houses. The Sun is like the houses; they are not moving. It looks to us as though the Sun is moving, but it's really the Earth that is turning around.

You can think of the Earth as an orange with a pencil through it.

The Earth spins like an orange on a pencil.

If you twist the pencil, the whole orange spins around. This is like the Earth spinning around. The pencil is called the axis of the orange. In the same way, we can think of an axis that goes through the Earth. The axis is a line that we can imagine, it is not a real thing. Earth spins around that axis. We say the Earth rotates (spins).

We say that the Earth has an axis that it rotates on. This axis runs from the North Pole to the South Pole as you can see in the picture.

Other objects also have axes of rotation. For example, an ice skater has a vertical axis that she rotates on when spinning on a spot during her performance.

A log which is floating in water can also roll around. It will have a horizontal axis of rotation.

Different axes of rotation

Make a model of the Earth in daytime and nighttime

MATERIALS:

a globe of the Earth or a balloon with the shapes of the continents drawn on it

string to hang a globe or balloon

a large mirror

INSTRUCTIONS:

Everyone must look at the globe from the same side. A globe is a model of the Earth.

This picture shows you how to set up the equipment.

Set up a mirror outside the room so that it reflects bright sunlight onto the Earth globe. Your globe must be able to spin around.

Everyone must look at the globe from the same side.

Find Africa on the globe. Turn the globe so that the Sun's light falls on South Africa.

One side of the globe is in shadow. Find the shadow in the picture. Write the word "shadow" next to it.

This is to make sure your learners are following the explanation.

Find where Durban and Cape Town are on the globe.

Make small people out of Prestik and stick their feet on the globe at Durban and Cape Town.

Look at the globe in the picture. If you were in Durban, would it be daytime or nighttime?

If you were in Cape Town, would it be daytime or nighttime?

Now turn the globe so that Africa moves to the right. That is, you turn the globe towards the East. You will see Durban becoming dark and moving into the shadow. When Durban is in nighttime, Cape Town will still be in sunlight.

Keep on turning the globe towards the East. Now Cape Town will go into the shadow. That is nighttime for the people in Cape Town.

Which city will come back into daytime first, Cape Town or Durban?

Skill: Predicting from the pattern they can see. Answer: Durban. We know that the Sun rises earlier in Durban than in Cape Town.

Keep on turning the globe to the East, and Durban will come back into daytime. You have to move to the other side of the model to see Durban move into sunlight.

How many hours pass for the Earth to turn around once?

24 hours. People did not discover how long an hour is; they decided how long an hour would be, and they divided up the day-night into 24 hours.

We see the Sun appear to rise and move across the sky every day. But the Sun does not really move; it only seems to move! Earth is spinning round and round, and we are moving around with the Earth. The Earth takes 24 hours to complete one full rotation.

Can you see how the light from the Sun only reaches one half of the Earth as it rotates?

Your head can be a model of the Earth

MATERIALS:

yourself

sunlight coming from one side

INSTRUCTIONS:

This model will help you to understand why we see the Sun move across the sky. Do this in the early morning when the Sun is still low.

We will say that your nose is Africa. You are on Africa. Look at picture below.

Using your head as a model of the Earth.

Now stand so that bright light from the Sun shines across your right cheek.

Turn slowly to your left. Turn your eyes towards the bright place where the Sun is. You will see the Sun move to your right while you move to the left.

Move your feet and turn further; you will see the Sun "go down" over your right cheek.

They must move their whole bodies around, not just their heads!

When you have turned your back to the Sun, you cannot see the bright light any more. That is like night time in Africa.

Turn further to your left and you will see the Sun "rise" over your left cheek. That is like sunrise in Africa.

NB. Make sure to emphasise to learners that they are moving their head around which is like the Earth rotating, whilst the light source (the Sun) does not move.

Revolution (Earth)

revolve

revolution

rotate

orbit

By now you know that all the planets revolve (travel) around the Sun. Each planet has its own pathway. This is called its orbit. We can also say planets orbit the Sun. Earth also moves in its own orbit around the Sun. This movement is called the revolution of the Earth around the Sun. We can also say that the Earth orbits around the Sun.

We have now come across two new words: rotation and revolution. Remember, these are not the same thing! Let's do an activity using our own bodies to understand the difference between revolution and rotation.

Most people, including adults, mix up the terms `revolution' and `rotation'. The simplest way to deal with this is to say that the Earth spins around its own axis, and it orbits around the Sun. We can use "orbit" as a verb. In the next activity, make sure to show the difference in the body movements when rotating and when revolving. Explain to learners when they are doing each one. This is also another way of making a model of the motions of the Earth. We did it before, with the ball swinging around on a long string.

Make a model of the Earth revolving around the Sun

MATERIALS:

room to move around

INSTRUCTIONS:

We are going to use our bodies to understand the difference between revolving and rotating.

First, the whole class must stand, and spread out. Now spin around with your arms out, staying on one spot. This is called rotation! The Earth rotates like this on its axis.

Now get into pairs. One learner must stand in one spot and the other learner must walk in a circle around the other person. This is revolution. The second learner is revolving around the learner standing still in the middle. The Earth revolves around the Sun like this.

Now, let's put both movements together! As the Earth rotates on its axis, it also revolves around the Sun. This might be tricky! Spin around (rotate) while also moving in a big circle around your partner (revolve). Look at the picture below.

The learner is rotating (spinning) and revolving around his partner.

QUESTIONS:

In this model, who represents the Sun and who represents the Earth?

Every 4 years we have a leap year, which is when there is one extra day in the year. This is because the Earth actually takes 365.25 days to revolve around the Sun, and not just 365 days. So every 4 years, we have an extra day to account for these quarter days.

The learner standing still is the Sun and the learner moving around is the Earth.

When you are spinning and walking in a circle around your partner, sometimes you face your partner and sometimes your back is to your partner. Which of these represents day for you and which represents night for you?

When you face your partner it is like day as the Sun shines on your face and when your back is to your partner, then it is like night.

You could spin around very quickly, but how many hours need to pass for the Earth to rotate once?

24 hours

You could also move around your partner quite quickly. In reality, how long does it take for the Earth to go once around the Sun?

365 days

Wherever we are, we can find the East - West direction by the place where the Sun rises and sets.

The Earth spins on its axis once in 24 hours. This spinning is called rotation.

The part of the Earth that faces the Sun experiences daylight, and the part that is turned away from the Sun experiences night.

The Earth travels in its orbit right around the Sun. This travel in orbit is called revolution.

A complete travelling of the Earth around the Sun makes a year.

How can you find East?

Look towards the place where the Sun comes up in the morning.

How can you find North?

Stretch out your arms so that your right hand point East and your left hand points West. Then North is the direction in front of you.

Why does it look as though the Sun moves across the sky when we know that the Sun does not move?

The Sun seems to move because the Earth is rotating (turning). The Sun seems to move from East to West, but that is because the Earth is rotating from West to East.

Where is the Sun, when it is nighttime where we are?

The Sun is on the other side of the world.

When we are having night, is everybody in the world also having night?

No

The Earth spins on its own axis. What term refers to this?

Rotate/rotation

The Earth and the other planets travel in an orbit around the Sun. What term refers to this?

Revolve/revolution

How many hours does it take the Earth to rotate once?

24 hours

How many days does it take the Earth to revolve once around the Sun?

365.25 days

Do you think Mars would take more Earth days to revolve around the Sun than Earth does? Why?

Yes, it would take longer because it is further away and therefore has a longer/bigger pathway.

Bonus question: Why do you think we have a leap year every 4 years and not every 3 or 5 years?

This is because it is 365.25 days. As our calendar only has 365 days, four quarters make up an extra day every four years. This might be quite hard as it deals with fractions.

The movement of the Moon

Does the Moon move around the Earth?

Has anyone ever seen the far side of the Moon?

What is a solar eclipse?

Rotation (Moon)

On Earth we see only one side of the Moon. Nobody knew what the far side to the Moon looked like until the Soviet Luna spacecraft went into orbit around the Moon in 1959 and photographed the far side. The force of gravity between the Earth and Moon holds the Moon's near side facing us.

Video showing the movement of the Moon http://www.youtube.com/watch?v=exIpL0Uhr_k&feature=related

This photo was taken by a spacecraft orbiting the Moon. It shows the far side of the Moon that we never see.

It is a very difficult concept to understand that we only ever see one side of the Moon, yet the Moon still rotates. The following dramatisation will help learners to understand this. Make sure that the ball being used has a clear mark on one side so that this can be used as a reference.

Does the Moon rotate?

MATERIALS:

a white ball with a red mark on it

a person who will swing the ball around like the learner in the picture

another person who will watch the ball as it swings around

INSTRUCTIONS:

Do as the learner in the picture is doing. Stretch out your arm and make the white ball revolve around your body by holding out your arm and moving on around on a spot.

As you are moving the ball around yourself, you only ever see one side of the ball. Do you agree?

Your partner must stand on one side of you as you swing the ball around. What does this person see? They will see different sides of the ball.

Take it in turns to be the one moving the ball around as you rotate and the one observing.

The learner represents the Earth and the white ball represents the Moon.

Do we always see the same side of the Moon? (video) http://www.youtube.com/watch?v=OZIB_leg75Q&feature=related

The learner swinging the ball always sees the same side of the ball, but a person standing watching the ball will say that it rotates. The red mark on the ball will point to the side of the room, then to the back of the room, then to the other side, and then to the front of the room.

So the person watching will say that the ball has rotated, and also revolved.

The real Moon takes about 28 days to rotate once.

Revolution (Moon)

The Moon also revolves in orbit around the Earth, as you saw in the last activity. The Moon takes about 28 days to complete one orbit. The force of gravity between the Earth and the Moon holds the Moon so that it always faces us on Earth.

The Moon revolves around the Earth.

For the following activity, divide the class up into groups. First let them discuss how they are going to act out the movement, using the knowledge and movements from the last two activities. They have to put these together. You can chose some learners as judges who decide which group understands the movements best. This activity requires learners to work in a group to come up with an answer and present it to the class. You can also get the learners to explain what they are doing as they are acting out to see if they really understand the movement.

Make a model of the Earth and Moon revolving around the Sun

MATERIALS:

a white ball

two people who have practised the model in the previous activity

INSTRUCTIONS:

You must use your bodies and the white ball to act out this model of the Earth and Moon revolving around the Sun.

Work together in small groups to decide how you are going to perform this model.

You must put together the movement of the Moon around the Earth from the last activity, and the movement of the Earth with its Moon, around the Sun.

Then perform the movements for the class.

So the model you must perform will be like this diagram shows.

Acting out the Moon and Earth moving around the Sun

The Moon travels in an orbit around the Earth in about 28 days.

The Moon rotates on an axis which also takes about 28 days.

We always see only one side of the Moon.

Together, the Earth and Moon revolve around the Sun.

Complete the sentences using all the words from the word box. write the sentences out in full on the lines below and number each sentence.

The Sun stays in _____

The Earth rotates on its own _____

The Moon revolves _____

The _____ revolve together in a big circle around the Sun.

We only ever see _____ of the Moon.

Word box

Moon and the Earth

around the Earth

one side

axis

the same place

Complete the table comparing the Sun, Earth and Moon. Some answers having been filled in for you.

Question
Sun
Earth
Moon

What is the object classified as?

a Moon

What is the shape?

What is the size relative to the other objects being discussed here?

The Sun is the biggest.

What is the movement in relation to other objects?

The Earth revolves around the Sun.

What is the object made of?

rock

Can this object produce light?

No, the Moon reflects the Sun's rays.

Is there water present?

Question
Sun
Earth
Moon

What is the object classified as?

star

planet

a moon

What is the shape?

round

round

round

What is the size relative to the other objects being discussed here?

The Sun is the biggest.

The Earth is bigger than the Moon and much smaller than the Sun.

The Moon is the smallest.

What is the movement in relation to other objects?

The Sun stays in the same place

The Earth revolves around the Sun.

The Moon revolves around the rotating Earth, while the Earth revolves around the Sun.

What is the object made of?

hot gas (mostly hydrogen and helium)

solid rock, magma, water and gases in the atmosphere

rock

Can this object produce (radiate) light?

yes

No, it reflects the Sun's light.

No, the Moon reflects the Sun's rays.

is there water present?

no

yes

no

Systems to explore the Moon and Mars

How to introduce this topic:

There is a strategic reason for placing this technology project on systems to explore the Moon and Mars here: if we leave this unit to the last 2 weeks of the year, the children will probably not get the experience of doing a technology project. They may just make a thing with wheels, in their own time, perhaps at home, and that is not technology.

The educational value in technology lies in the investigating, thinking and designing that children must do. Technology aims to make children capable; capability means the children's ability to turn thinking into doing and completing. When they learn new science knowledge, the learning has a purpose: they must use that knowledge in producing good designs. when they have made a product, they should be able to explain to you all the reasons why they designed it like that (even if they could not make it in the way they wanted to).

So some very important learning happens during a technology project, and you need to guide them through all the stages. That's why we don't leave technology projects for the last weeks of the year.

If you trained as a technology teacher, you will recognise the NCS pattern of technology projects - do you remember IDMEC? You can remind the learners of this:

I stands for investigating the problem which some people have, investigating existing products, and investigating concepts and skills that you will need to solve the problem.

D stands for designing - that means using what you learnt from investigations to think of good ways to solve the problem.

M stands for making - when you make your model, you use materials and tools, you make your model look good, and you show the teacher what you learnt in your investigating." (notice that most children design with their hands, not only with pencil and paper. As they work with materials they get more ideas, and their design improves. As a result, we should expect them to go back and forth between designing and making. It's really all the same stage of a project.)

E stands for evaluating - after you have made your model to solve the problem, you have to ask, does it work? is this what the people wanted? could we make a better one?

C stands for communicating - you must show other people how you decided on your solution to the problem. you need to write and draw your ideas." (the learners should be drawing and writing all through the project. don't leave the writing to the end, because they find it boring at that stage. When they are getting new ideas they often enjoy writing because they are writing about their own ideas; this is a great strength of technology in school. a technology project gives the children reasons for reading and reasons for writing. and so - this is very important - we can address the literacy problem through the subject of Natural Science and Technology.)

How do we make a vehicle move on the Moon or Mars?

How do we collect information about the rocks on the surface?

What do scientists want to know about the Moon and Mars?

Vehicles used on Mars

No humans have ever been to Mars but scientists know a lot about the surface of Mars. You learnt about this planet in the first chapter. They have found out what Mars is like by using vehicles called rovers that send back information to Earth. Let's have a look at some of these different rovers and how they operate.

The Pathfinder rover

In 1997, the Pathfinder spacecraft landed on Mars. It had a small rover inside; the Pathfinder opened up and the rover came out and began taking photographs of Mars. Look at the picture below. The photo is not very clear but remember that it was taken with a robot camera; that camera sent the picture by radio signals, back to Earth.

Mars

rover

microbes

This is the rover that was carried by the Pathfinder spacecraft. It has instruments to find out what the rock is made of.

The driver of the rover was millions of kilometres away on Earth and used radio signals to steer the rover.

Photo means "light" and voltaic means "electricity". So photovoltaic means producing electricity using light.

The Pathfinder rover used electric motors to move. The electricity for the motors came from photovoltaic (solar) panels on its top surface. Solar panels transfer energy from sunlight to the electric motors. Find the solar panels in the photo. The solar panels that you learnt about in Energy and Change last term are also photovoltaic panels.

The rover was about 630 mm long and 480 mm wide. Imagine you are looking down at the top of the rover. Use your ruler to draw a rectangle that size on the board. Then draw the wheels you could see.

Let a learner representative from three groups each do a drawing on the board at the same time; the class will be interested to see who does it best. A good answer will show a rectangle 630 mm x 480 mm, and then six small rectangles for the wheels. From the top, the wheels will not be circles - let the learners confirm this by looking down at a shoe polish tin or snuffbox.

The rovers called Spirit and Opportunity

These two rovers landed on Mars in 2004. Like Pathfinder, they also used solar panels that generate electricity from sunlight. In 2010, after 6 years, the rover called Spirit got stuck in sand. Soon after this it stopped sending back messages.

The rover called Opportunity is still working, after 9 years on Mars! It has travelled over 35 km and sent back thousands of pictures.

Opportunity's mission (video) http://www.youtube.com/watch?v=_5sChMVz8v4&feature=player_embedded

The Opportunity rover is going to scrape some grains off that rock and analyse it.

The rover called Curiosity

The making of Curiosity (video) http://www.nasa.gov/multimedia/videogallery/index.html?collection_id=18895&media_id=144485271

This rover is the size of a small car and will be able to travel further and collect much more information about the surface of Mars. Scientists want to know whether there are any living things on other planets. So the rover will look for signs that microorganisms lived on Mars a long time ago. Microorganisms are very tiny organisms that cannot be seen by the eye. They are so small that millions would fit onto the tip of a needle.

The Mars rover called Curiosity

The rover has video cameras to show the driver back on Earth what is in front of the rover, and it has a long arm with a scoop to pick up soil samples. It also has a laser that can heat rock until it turns into vapour. Then special cameras look at the vapour and find out what substances are in the vapour. Can you see the cameras in the picture?

Teaching Curiosity to use a robotic arm on Mars (video) http://www.nasa.gov/multimedia/videogallery/index.html?media_id=139932591 and

Do you think that there could be living things on Mars? What do living things need to go on living?

Water, something to feed on for energy, and perhaps they need oxygen.

The wheels of Mars rovers

INSTRUCTIONS:

Look at the wheels of three Mars rovers below.

Answer the questions.

The wheels of three Mars rovers

Landing Curiosity on Mars (video) http://www.nasa.gov/multimedia/videogallery/index.html?collection_id=18895&media_id=144485271 and http://www.youtube.com/watch?v=_qaaj69MKrU

QUESTIONS:

We know that wheels are round. Why do these wheels look like rectangles?

The wheels look rectangular because we are seeing them in front view, not side view. Learners will need to know about front, side and top views for drawing in Technology.

The diameters of the three wheels are 13 cm, 30 cm and 45 cm. Draw three circles on the board or paper to show these diameters.

Learners can use a piece of string as a compass; they tie a knot at one end and hold the chalk at half of the diameter. For example, to draw a circle with 30 cm diameter, the chalk must be 15 cm from the knot. Then they keep the knot in one spot on the board and move the chalk all around the knot. The string keeps the chalk at 15 cm from the knot. The knot is on the centre of the circle, the length of the string is the radius (i.e. 15 cm), the path of the chalk is the circumference and the distance across the circle, through the centre, is the diameter (two times the radius).

The wheels shown belong to the rovers, Pathfinder, Opportunity and Curiosity. Match the wheels to the rovers. Write the letters A, B and C below with the name of the rover next to it.

A: Pathfinder

B: Opportunity

C: Curiosity

Why are the wheels different diameters?

The wheels are different sizes because the rover cars have gotten bigger and bigger, so they need bigger wheels.

Why did the designers choose such wide wheels?

The designers probably chose wide wheels because the surface of Mars is sandy. A narrow wheel, like a bicycle wheel, would sink into the sand.

Use your ruler and work with the picture of the 3 wheels. Measure the diameter of each wheel in the picture and the width of each wheel. Write your measurements into this table.

Diameter of wheel

Width of wheel

Pathfinder

Opportunity

Curiosity

What is the pattern that you find? Write out the whole sentence The bigger the diameter, the ...

The bigger the diameter, the wider the wheel. They can see the pattern in the picture, but they need to learn the language for describing patterns: The bigger..., the wider...

Vehicles used on the Moon

Apollo 11 mission astronauts walked around on the Moon. This was the first time. But for Apollo 15, 16 and 17 each mission had a lunar rover called a Moon buggy. Lunar means "relating to the Moon".

Look at the picture of the lunar rover. This vehicle went to the Moon in 1972 and it is still there. Other spacecraft photographed it in 2011. You will find out more about this rover when you investigate rovers for your Technology project.

lunar

mission

astronauts

The Apollo 17 astronauts drove this lunar rover on the Moon.

Astronauts testing out a lunar rover on Earth

Below is a photograph of astronauts testing out a lunar rover on Earth before they used it on the surface of the Moon.

Footage from the first landing on the Moon (video) http://www.youtube.com/watch?v=PrSD8tpoSz0&feature=related

Design and make a vehicle to collect Moon rocks

kinetic energy

potential energy

engineer

Do you remember how, in the last term of Gr. 4, you were on your way to the Moon? You are now part of a crew in the Apollo scientific mission.

We are approaching the Moon!

Investigate the need for a Moon rover

Set the scenario of a mission to collect Moon rocks. This follows on from the Gr. 4 Technology project where the task was to design and build a rocket to get to the Moon.

Your mission is to collect rocks from the Moon. Scientists back on Earth want to study those rocks and find out whether they are the same as rocks on Earth. You have to collect from different places on the Moon so you need to be able to move around on the surface.

In 1972, scientists really did go to the Moon to collect rocks. In the picture you see a photo of one of the rocks that came back to Earth with the Apollo 16 Mission.

Apollo 17 Lunar Rover (video) http://www.youtube.com/watch?v=0_YhYBxjpQU

A rock from the Moon

The Sun heats the Moon's surface to the temperature of boiling water so you will have to wear a special suit to protect you and cool you. The suit will make it difficult to work and walk.

The Moon has no air, so you will have to carry air for yourself in tanks (bottles). To do all this work, you will need a vehicle to move around on the Moon. The vehicle is called a rover.

Astronaut Ceman and Schmitt practising to pick up rock samples before going on the Apollo 17 lunar mission

Astronaut Schmitt collecting samples on the Moon

Your Design brief

A Design brief for a Technology project is a short statement of what you are going to make, why you are going to make it and what you are going to make it for.

Question:

Write your Design brief in the space below using the following phrases:

"I am going to design and make a …."

"that will help scientists to …"

"....the Moon"

Now that you have specified your Design brief for your project,we need to do some more investigating to answer some questions before we can start designing.

Investigate the surface of the Moon

In Chapter 3, you learnt about the Moon. The rover needs to be able to drive over the Moon's surface, so we must investigate what the surface of the Moon is like.

Write one fact about the Moon that you must think about when you design your rover. Write a sentence to explain why that fact is important.

For example, the Moon is covered in loose dust (so the wheels must not sink in and get stuck). The Moon has craters (so the Moon rover must be able to go into a crater and come out again). There is no air on the Moon so a petrol engine will not work in the rover.

Investigate ways to move people and equipment

The rover on the Moon had four electric motors; one motor in each wheel. It did not need a steering wheel, because the driver can switch the motors on and off in each wheel. This steers the vehicle. It had two seats with seat-belts.

Astronauts used this rover on the Moon during the Apollo 17 mission.

The part that looks like an umbrella is an aerial that picked up radio messages from Earth. Can you see this in the picture? It looks a bit like a satellite dish you see on some houses for television.

How do you think the rover got energy to work the motors in the wheels?

It had to carry batteries to provide energy to the motors.

The rover was made of very light materials. Why did the rover have to be light?

Firstly, a rocket had to lift it off the Earth to go to the Moon; secondly, a light vehicle could work on smaller batteries.

Why did the wheels have shields over them? The shields are the orange things over the wheels.

The tyres could throw up small stones that could do damage.

The wheels of the rover were quite wide. What would happen if the wheels were narrow like a bicycle wheel?

The wheels would sink into the sand and get stuck.

Why must cars on Earth have headlights?

Cars on Earth have headlights so that the drivers can see the road at night.

Do you think the rover needed headlights?

No, the astronauts worked in full sunlight.

Investigate ways to give energy to the rover

Your Moon rover needs energy to make it move. Do you remember that in Gr. 5 we looked at Energy and Movement when doing Energy and Change?

This is quite a difficult topic and you will learn more about it in later grades, so let's refresh some of these terms.

When you stretch an elastic you transfer energy to it, called stored energy. Another way of saying this is that you give the elastic potential energy. This means it has the potential to do work. Or in other words, in the future the stretched elastic band can do something.

This stretched elastic band has potential (stored) energy.

When you let the stretched elastic band go, it now moves as it springs back. This is movement energy, and is also called kinetic energy. Kinetic means movement. The potential energy stored in the stretched elastic band changed into kinetic energy as the elastic band was released and moved.

Now let's apply these terms to the rover. You can also give something potential energy by lifting it up off the ground as it then has the potential to fall or move back to the ground. You can give energy to your Moon rover if you lift it up on a plank, as you see in this picture.

One way to give your rover energy to move

When you lift up the plank and rover, your hand gives some of your energy to the rover. It now has potential energy to move.

When you let the rover go, what will happen? Use the words "kinetic energy" in your answer.

The rover will lose potential energy and gain kinetic energy as it moves down the ramp. This might be quite difficult for some learners to answer if they have still not understood the topics. Perhaps answer the question as a class discussion.

The plank is useful for testing the wheels of your model. But the rover must be able to go up hills, not only down them.

The second way to give your rover energy to move is to use an electric motor and battery. Do you remember last term we looked at electric circuits and the source of energy for a circuit is a cell or battery? You can fit an electric motor and a battery to your rover. The potential energy in that system is in the battery.

A battery is a source of potential energy for an electric motor. http://www.flickr.com/photos/razor512/2109796582/

Another way to make your rover move on the Moon is to use a rocket. Rockets will work on the Moon. Inside the rocket, gas pushes against all the sides. Some gas pushes against the walls of the balloon and some gas pushes out through the opening of the balloon.

Look at the rocket car in the picture. The gas pushing through the opening of the balloon pushes the whole car forward.

The balloon works like a rocket. You have to give it potential energy first.

This rocket is on rollers. Could you fit wheels to this car?

The real Moon rovers had batteries and electric motors in each wheel. Many electric cars have a motor. This motor can give energy to your Moon rover.

Investigate ways to make a body with wheels

Your Moon rover needs a body for the scientists to sit on and to put the rocks into. The body of a vehicle must have good ways to hold the wheels.

We looked at wheels and axles in Gr. 5 in Energy and Change. A wheel fits onto an axle, which is a solid rod or bar that allows the wheels to turn.

Label the two wheels and the axle in the following diagram.

You know there are different ways to let wheels turn on an axle. One way is to have the axle fixed to the body, and the wheels are free to turn on the axle. What is the other way to let wheels turn?

1) Wheels fixed to the axle

You can use plastic straws or the barrel of a ballpoint pen to make a bearing for an axle. The picture shows you two ways to fix the bearings onto the body. The bearing is the hollow tube that the axle goes through. The bearing must be bigger than the axle so that the axle can turn easily.

Two ways to fix the bearing onto the body

What are the two ways used in the picture to fix the bearing onto the body?

Tape and glue

What are some materials that you could use to make the axle in the above picture?

Smaller straws, dowel sticks, sosatie sticks, etc.

You can also use plastic signboard or strong corrugated cardboard to make a body with wheels. Can you see how the axle goes through the holes in the cardboard?

The board makes bearings for the axles which are fixed to the wheels. The axles turn in the holes.

2) Wheels turn on the axle

The next picture shows you another way to let the wheels turn. This time the axle remains still and the wheels turn on the axle. The axle is fastened to a wooden body with cable clips. Cable clips fasten telephone cables to walls. Can you see the blown up version of a cable clip? The clips may hold the axle tightly, so the wheels must be free to rotate.

How the cable clips can hold an axle

A clip to hold telephone cables to the wall

Designing and Making

Your Moon rover can look different to the Apollo rovers.

One of the astronauts driving a Moon rover

The Apollo engineers designed other rovers, but in the end they chose this design. Your design will look different to their designs.

An engineer is someone who designs and builds machines and structures for a living. If you enjoy the Technology projects then maybe one day you could be an engineer!

Designing and making your rover

SPECIFICATIONS ( what your rover must be like):

Your rover must be balloon powered.

Your rover's wheels should be able to roll easily and it should go at least 2 metres on the floor.

Your rover must have two seats and it must have a model of you as a Moon explorer.

It must be able to carry two small stones for at least 2 metres. The stones represent rock samples from the Moon, to take back to Earth.

CONSTRAINTS:

You must build your rover in class.

DESIGN:

Draw a picture of a rover you could make in the space below.

Show the seats, with an astronaut in one seat. Show the place where the Moon rocks will go.

Add other parts that your rover should have. Write labels to tell everyone what the different parts of the rover are.

Leave some space at the bottom for a second design. When you begin making the rover, you will get better ideas. Then you can draw another picture of your design. The two pictures will show how your ideas changed.

MATERIALS:

Things to collect for wheels:You can collect snuffboxes, shoe-polish tins, the lids of bottles. You can also cut out cardboard circles.

Things to collect for axles:You can find sosatie sticks, stiff plastic straws, wooden dowel sticks, aluminium rods. The school may have plastic rods from a supplier. You can also use nails or wire to make axles.

Things you can use for wheels and axles

Tools and materials you need as a class:

some long-nose pliers to cut and bend wire

hole-makers (small and big nails) and big scissors for cutting cardboard

a small hammer to drive the nails

some glue (or you can make flour glue in class)

balloons to power the rover

To decorate your rover car you need crayons or paint. Remember to colour the scientist who drives the rover.

MAKE:

Now let's make the rover. Below are some tips which will help you when making your rover. Remember that you may not have the perfect design from the start! So when making your rover, you need to go back and modify your design as you find things which work and do not work.

1. How to find the centre of a wheel (remember, a wheel is a circle)

Some plastic lids have a small dimple or lump that shows you where the centre is.

If your lids or discs do not have a dimple, you can use a ruler to draw diameter lines across the middle (a dimple is a small dent).

A diameter line is the longest line you can draw across a circle. Where diameters cross, that is the centre.

A wheel is a circle. Draw three diameters and mark the centre. In this example the centre is the red dot.

2. How to make the right size hole in the centre

If you want the wheel to rotate on the axle, then you must make a hole that is a little bit bigger than the diameter of the axle.

If you want the wheel to be tight on the axle, then you must make a hole that is smaller than the diameter of the axle. When you push the wheel onto the axle, it will grip the axle.

3. How to stop wheels wobbling on their axles

If the axle goes through just one surface of the lid, this is what can happen: the wheel will wobble. You need to give the lid another surface. Glue two lids together.

Or else, trace the shape of the lid on cardboard, mark a hole in the centre of the circle, and cut out the cardboard. Cut the cardboard so that the disc will be a tight fit in the lid. Then glue the cardboard into the lid.

You can stop the wobbling by glueing two lids together.

4. Does the wheel rub against the body of the rover?

You need a spacer on the axle, to keep some space between the wheel and the body.

You can use a bead with a large hole, or you can make plastic washers from slippery plastic. Milk bottles are good for making slippery washers.

Use an office punch for making neat holes in a piece of milk-bottle plastic. Then cut around the holes to make washers.

Where to use a spacer or washer

5. Does the wheel come off the axle?

Push a piece of soft tubing onto the end of the axle as you see in the picture.

Or push on a flat piece of cardboard and hold it on the axle with glue.

Soft plastic tubing or glue will stop the wheel coming off the axle.

6. Does the rover not run in a straight line?

The axles of your rover must be parallel.

These axles in the picture are not parallel. If your axles go through the body, then the axle holes must be the same distance apart on the left and the right side.

If you need to make a hole in a new place, then you can glue a small piece of card with a hole in it over the old hole.

These axles are not parallel so the rover will not go straight.

Test your rover and make it run as well as you can. Go back and draw your improved design. Draw the rover you have made and write labels to explain what all the parts do. For example, you can write "This piece of straw stops the wheel rubbing against the body."

EVALUATE:

At this point in a technology project, you stop and ask yourself, did we do a good project? Did we make something that solves the problem?

Clear an area in the classroom to show the class's Moon rovers. Show your group's Moon rover. Show how it moves by itself or how it rolls down a sloping plank.

Discuss these questions in the class for each Moon rover:

What were the specifications for the Moon rover?

Does the rover have a model of the astronaut sitting on it?

Can your rover carry small Moon rocks back to your Moon lander?

Does your rover have a hinge anywhere in it?

Do the wheels roll easily?

Can your Moon rover go 2 metres?

Whose rover rolls the furthest?

Does it roll in a straight line, or does it roll in a curve?

Did you need to make the body of the rover stronger? What did you do to make it stronger?

If you really had to go to the Moon, what would you need on a real rover car?

Write down how far each Moon rover from each group can go after it rolls down the plank. You now need to draw a bar graph to present this data (information) in the space below. Your teacher will help you to get started and then you can finish drawing it yourself.

Take the learners through how to draw a bar graph, step by step. Explain why a bar graph is used and not a line graph for example. A line graph is used when a single variable is tracked against a series of known quantities. For example, in this case, if learners were to use one rover and test how far it went when they changed the angle of the plank, then a line graph would be used. You can do this as an extension to show the difference between the graphs.

On the other hand, a bar graph is used when there are two or more things being measured or counted. In this case all the rovers are being measured. They are not related to each other so you cannot draw a line between the points. But rather a bar graph is used to compare the measurement for each object.

The objects being measured must go along the horizontal x-axis (independent variable) and the distance moved must go on the vertical y-axis (dependent variable). You can assign each group a number to plot on the x-axis or allow them to come up with their own names for their rovers.

Record all the results in a table on the board with the group name/number in the first column and the distance moved in the second column. You can then draw the axes for the graph next to this table so that learners can see that the information from the table is now presented differently as a graph, but it is the same information. You can draw the bar for the first group and then let the class finish drawing the other bars. Make sure to walk around the class while learners are completing this.

Although learners do not need to know the terms independent and dependent variable, they need to start learning about different types of graphs as they often battle with this in the later grades.

After you have tested and evaluated everyone's rovers as a class, use the following space to write an evaluation of your own rover. Remember to answer the questions above when evaluating how successful your rover is.

Below is a summary of some of the things that we learnt from doing this project:

Axles must be parallel for the car to run straight.

Axles can be fixed and wheels free to turn, or the axle can turn with the wheels fixed to it.

Axles turn in bearings. Bearings let axles turn freely.

A car must have energy from some source. The source can be a hand that lifts the car up to the top of a ramp, or the source can be a falling weight, or the source can be rubber bands or a blown-up balloon.

Scientists send vehicles to explore the surface of moons and other planets.

These vehicles have radios that send back information to scientists on Earth.

The vehicles need special wheels to move across the sand and stones.

People have been to the Moon, but no people have yet been to Mars.

Only vehicles (robots) operated by people back on Earth have been sent to explore the surface of Mars.

Give three names of vehicles used on Mars to explore the surface of the planet.

Pathfinder, Opportunity, Curiosity, or Spirit

Which of these vehicles is the most recent one to go to Mars?

Curiosity

Why do people need Moon rovers when they are exploring the surface?

They need them so that they can cover greater distances. They also collect rock samples and so they need the rovers to carry the samples back to their spacecraft.

What is the main difference between vehicles used on the Moon and vehicles used on Mars to explore the surfaces? Hint: This has to do with whether people have visited the Moon or Mars.

Rovers used on the Moon are driven by people on the actual rover. People have never been to Mars so these vehicles are operated by people back on Earth.

What is the name given to the solid bar that connects two wheels?

An axle

Describe how you made sure that your Moon rover went straight and that the wheels did not fall off.

Learner dependent answer

Why do you think the human race is so interested in exploring other planets and objects in our solar system?

This is a learner dependent answer. (Answers can include something about looking for signs of other life, discovering what makes Earth unique, pure scientific interest, etc.)

Systems for looking into Space

The stars we see at night - are those all the stars there are?

How do scientists find out what stars are like?

How come you can't see other planets when looking up at the sky, but we have some beautiful close-up photographs?

Telescopes

The telescope was first discovered by the Dutch. In Holland, a lot of the people were sailors and sea-explorers so they used their telescopes at sea to see if ships far away on the horizon were friends or maybe pirates.

A telescope makes faraway things look bigger and closer.

bright

dishes

distant

faint

lens

magnify

Milky Way

phases

reflect

Square Kilometre Array

radio waves

Here is an introduction you can use with your learners. From the earliest times that people could look and wonder, people have looked up into the night sky and wondered what the bright things up there are. They could see how these things moved but they did not know how far away they were or what they were. They knew that the planets are different to the stars. The stars always stay in their same patterns, but the planets move closer to a star each night, and then further away.

Galileo Galilei was a professor of mathematics at the University of Padua, Italy. In 1609 he heard that somebody in Holland had made a telescope, and he worked out how to make one himself.

Galileo Galilei's telescope looked like this. It could only see a small part of the sky at a time. http://commons.wikimedia.org/wiki/File:Tel_galileo.jpg

Galileo Galilei showing his telescope to a group of scientists

Galileo got into trouble with the authorities because they did not like what he wrote. They taught that the Earth was the centre of the universe and the Sun, Moon, stars and planets all revolved around the Earth. Galileo told people that was not true, and so he was put in jail.

Galileo used his telescope to look at the planets in the night sky, and he made careful notes of what he saw there. He was the first person to see that Jupiter had moons. He saw that Saturn has rings and he saw that Venus has phases like the Moon has. He also used his telescope to show people that the Milky Way was really made of billions of stars. He wrote books that taught people about telescopes and what they could show us in the night sky.

People can now buy telescopes like this to watch the stars from their own backyards. http://www.flickr.com/photos/ryanwick/3461850112/

The Hubble Space Telescope Story http://www.nasa.gov/mission_pages/hubble/story/the_story.html

Nowadays there are big telescopes in many parts of the world, and these telescopes have cameras to photograph the sky.

This photo of the sky was taken through a telescope. Each point of light is a star.

If you are based in Cape Town, you can take your learners to visit the South African Astronomical Observatory (http://www.saao.ac.za/) and if you are based in Johannesburg you can go on a tour of the Johannesburg Observatory http://www.saasta.ac.za/index.php?option=com_content&view=article&id=73&Itemid=63.

The biggest space telescope in the world is the Hubble Telescope, named after Edwin Hubble who first showed there were other galaxies besides our own, the Milky Way.

Telescopes have shown us that there are thousands of millions of stars that we could not see with our naked eyes. Some of those stars are so far away that their light has been travelling for millions of years to reach us.

The Southern African Large Telescope

One of the biggest telescopes in the world is here in South Africa, near the town of Sutherland. The telescope is called the Southern African Large Telescope or SALT. The telescope uses lenses and a very big mirror to see the stars and take photographs of them.

Real-time views from webcams at SALT http://www.salt.ac.za/html/webcam.html

This is SALT. Here the roof is closed, but at night it opens so that the telescope can see the sky.

This photo is taken from inside the dome of SALT and shows the large mirror.

Point out to learners in this photograph of the SALT mirrors that each mirror is a hexagon shape (like a beehive) and each mirror focuses the light onto a single spot. The learners will see how to do this in the next activity. When doing this in the activity with all the mirrors outside, bring back their attention to this image of the mirrors and the similarity.

The South African Large Telescope (video) http://www.youtube.com/watch?v=PkQbkuansGg

Work in groups for the next activity as it may be hard to source enough materials (lenses and mirrors) or each learner to be able to do the activity by themselves.

How lenses and mirrors make telescopes work

MATERIALS:

Each group needs a lens. You can use hand-lenses, or round empty bottles with water in them. Or you can use the glass part of a light bulb, full of water. Your teacher will show you how to remove the inside parts of an old light bulb.

Each group needs a mirror. It can be a small mirror, or you can make a mirror. You can glue the shiny foil from a potato-chip packet onto cardboard.

To make a lens from a light bulb, heat the metal cap of a dead light bulb in a flame. Then carefully lower the hot part into cold water so that the cold water just reaches the glass. The glass will crack around the metal cap and the insides of the bulb will fall out into the water. This will leave you with the ball-shaped glass part. If you fill it with water, it makes a good lens with a short focal length.

Put masking tape or Elastoplast on the broken edge of the glass to prevent children cutting themselves. Of course, we are talking about bulbs with a filament, not the new fluorescent energy-saver bulbs.

A lens can make things look bigger.

If you look through a bottle or glass full of water, you will see how it makes things look bigger.

INSTRUCTIONS (Part One):

Hold up the lens and look at something on the wall. You can look at a poster, for example.

If you are far away from the wall, the poster will seem to be upside down.

When you come closer to the wall, the poster will be right way up and bigger. The lens is magnifying the poster (to magnify means to make bigger).

QUESTIONS:

What do you notice about the shapes of lenses?

They have curved surfaces.

Why do you think this shape is necessary for the lens?

The light must pass through a curved shape so that the light bends; when the light from an object has come through the curved glass we may see the object enlarged (looking bigger). The curve makes the object look bigger as the light is bent.

INSTRUCTIONS (Part Two):

Now the class must go outside into the sunshine. Take the lens and your mirrors with you. This will work best on a hot, clear day.

Your teacher can point out a place on the wall that is in the shade.

Make a chalk circle on the wall, about 15 cm in diameter. The learners must aim at that circle.

Use your mirrors to reflect sunlight onto that spot.

The class can spread out; it does not matter where you stand. Just make sure you move your mirror so that it helps to light up the spot your teacher showed you.

If everyone reflects sunlight onto that one spot, it will become very bright there.

Light from all the mirrors goes to one shady spot on the wall.

QUESTIONS:

How could you make the spot brighter?

Ask them to make a prediction - they must say what will work to make the spot brighter. Answer: The class can use even more mirrors.

Will the spot feel hot? Make a prediction. (To "predict" means you say what is going to happen.)

How will you find out whether your prediction was correct?

For example, get a report from one person who goes to put her hand there.

The Sun does not give us only light. It also gives us heat. You know that if you stand facing the Sun with your eyes closed, you can still feel heat from the Sun on your face.

How could the class make the spot hotter?

Now that we have the class outside with mirrors, let's use the opportunity to teach about radiation and solar cookers. The Sun radiates electromagnetic waves with many frequencies. Our eyes respond to some of those frequencies and we see light. If the frequency is a little lower, our eyes cannot respond (we don't see it) but our skin responds and we can feel the radiation. These lower frequencies are called infrared radiation.

Answer: The class can use even more mirrors.

Can you make it even hotter by passing all the sunlight through a lens, onto the wall?

You should try this with the class. You will need a large hand lens about the size of a saucer. Move the lens until the spot of light on the wall is as small as you can get it. Let one of the learners put his hand in the spot and feel it. (It's unlikely to burn him.)

INSTRUCTIONS (Part Three):

Put a candle inside a glass jar and put on the lid.

Put the candle inside the jar to ensure that the warm air is not blown away from the candle and that it does not escape by convection. Here we are extending the activity beyond telescopes to let the learners think about solar cookers. In Gr. 5 they will have seen solar cookers - you can show them a picture of one and let them note how large the reflector is. The larger the reflector, the more energy the cooker can put into the food per second.

Can you melt the candle by using your mirrors?

The class should be able to do this if they have enough mirrors. They must hold the mirrors steady and not wobble them around.

Can you melt chocolate by using your mirrors?

Try this if they cannot melt the candle. Just decide who will get he melted chocolate afterwards!

All the mirrors work together like one big mirror, even though they are far apart. They all collect a little bit of energy from the Sun and send it to the bright spot.

The mirror of a telescope works like that. The light from some stars is very faint because the stars are very far away. But the big mirror collects all the faint light and focuses it to one lens. Then the telescope can gather (put together) enough light from the star to get a photograph of the star.

The Square Kilometre Array (SKA)

The SKA is a different kind of telescope for looking at the stars. Stars send out energy in light but also in radio waves. The SKA will receive radio waves that our eyes cannot see.

The SKA website has many resources to access to facilitate your class discussion of this project (http://www.ska.ac.za/learn/index.php). Do you remember the notes above that the Sun radiates at many frequencies? Some frequencies we can see, others we can only feel. There are many other frequencies that we can't detect, unless we have a radio receiver.

An array means a large number of the same items. For example, when the desks in your classroom are all lined up neatly, we can call that an array of desks.

The SKA will have an array of several thousand dishes like those in the picture. When you add together the area of all the dishes, the total area will be the same as one square kilometre. A square kilometer is an area in the shape of a square and the sides are each 1 km long. The area of the square will be 1 km2. That is why the telescope is called the Square Kilometre Array.

Sound waves must have something like air or water to travel through, but electromagnetic waves can travel through empty space.

This is how the SKA will look once it has been built. (Credit: SKA Organisation)

SKA video http://www.youtube.com/watch?v=0mfXKXVWG1s&feature=player_detailpage

There was actually a contest between South Africa and Australia to see who would host the SKA. Both countries really wanted it and the bid and voting went on for 9 years. Then at the beginning of 2012, it was announced that it would rather be hosted in both countries, but the larger portion of the dishes is to be in South Africa and Africa.

The dishes in the picture look like the satellite TV dishes that you see on some people's houses. Those dishes collect the weak TV signal that comes from a satellite high up in Space.

In the SKA, each dish collects a little of the radio signals that come from the stars, and sends it to a computer. The computer puts together all the signals to make a new picture of that star.

Scientists from many countries are working together to build the SKA in the Northern Cape. Most of the telescopes will be near the town of Carnarvon.

Some of the dishes will be very far away from Carnarvon. They will also collect signals from stars and send them to the computer in Carnarvon. This helps to improve the quality of the image that gets generated by the computer. Some dishes will be in Ghana, Zambia, Mozambique and Madagascar.

SKA will be the world's biggest and most sensitive radio telescope in the world. It will be finished in the year 2024.

Some of the dishes will be far away from Carnavon, in other countries across Africa, as well as Australia and New Zealand. (Credit: SKA Project South Africa)

The SKA

INSTRUCTIONS:

Look at the pictures of SKA in the text before.

Answer these questions.

QUESTIONS:

How is the picture of the SKA dishes like the picture of the class using mirrors to make a bright spot on the wall?

It has many dishes, like the many mirrors that the class is using.

Why does the SKA need so many collecting dishes?

The signal from some stars is very weak.

Why does it help the SKA to have dishes far away in Ghana, Kenya, and Mozambique?

How many dishes will be in Madagascar?

Madagascar will have two dishes, but assess whether the learners can find Madagascar on the map.

The SKA will be able to pick up signals that stars sent out thousands of millions of years ago. The signals have been travelling through Space for all that time. When the SKA picks up those signals, we will learn something about that time when the universe began, thousands of millions of years ago.

The objects we see in the sky are very far away.

We can use telescopes to see them more clearly, and to measure how far away they are.

Lenses can focus light to make a clear image.

Mirrors help to collect more light when stars are very faint (not bright).

What does a telescope do?

It makes faraway objects look closer.

Before Galileo, nobody knew that the planet Jupiter had moons. What was the reason?

The moons were too small to see with the naked eye, but Galileo's telescope made them big enough to see.

What does SKA stand for?

Square Kilometre Array

Why are the words "square kilometre" in the name?

The areas of all the dishes will add up to an area of one square kilometre.

With a telescope we can see very, very many stars. Why did we not know about all those stars before there were telescopes?

Those stars are too faint to see with the naked eye.

Astronomers build their telescopes far away from cities. Think of a reason why they do this and write it down.

The bright lights of the city make the sky bright and so it is harder to see the stars.