reflect
To bounce back from a surface, e.g. light is reflected back from a shiny surface.
Energy and Energy transfer
- What do we need energy for?
- Where does energy come from?
Energy for life
Scientists say energy is the ability to do work. We need to understand what this means. A way to think of it is that energy can make something happen.
Energy is the ability to do work
The idea of this activity is to have some fun playing a game so that the learners are tired afterwards. You can then introduce the idea that they used energy to run around - energy is the ability to do work and move.
Let us have some fun playing a game!
INSTRUCTIONS:
- Divide into groups of six and go outside for 10 minutes to play "Hide and Seek".
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These are the rules of the game:
- One person needs to be the seeker.
- The seeker needs to find a home - a tree or the wall will work well.
- The seeker closes their eyes and counts to 20.
- Everyone else must hide. They are the hiders.
- When the seeker has counted to 20, (s)he must find the others and tag them by touching.
- If the hiders can get to the seekers' home without him or her seeing them, they can block themselves and cannot be tagged by the seeker.
- If the seeker finds a hider s/he runs to their home, touches it and says "1,2,3, Tag Emma!" (or whoever they saw).
- If there is time left over, you can choose a new seeker and play again.
- Return to class after 10 minutes and talk to in your group about how you feel.
- Each group must choose a leader who will report back to the class.
- Write down the words that are being used to describe how you are feeling after the game.
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Write down some of the descriptive words below.
This game requires that you do a lot of running. You might even get tired from it. This means that energy is being used to do work.
Discussion questions for the teacher to raise with the class after this activity:
- Why do we need energy?
- Where do you get your energy from?
- What other things have energy? (other animals, plants, machines, houses and cars)
- Where do these things get their energy from?
- What would happen without these sources of energy?
We saw that we got tired from running and playing a game in the last activity. We use energy for everything we do.
Yes, that is right Jojo! Everything you do needs energy.
Energy is all around us.
INSTRUCTIONS:
- Think about what you do from when you get up in the morning until you go to sleep at night. Think about what happens around you everyday.
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Write down five things that you have thought about that you could not do without energy.
Teachers may ask learners to do this activity in groups and get each group to make a poster or do a short presentation to the class
In our daily lives, there are many things that we do that need energy. As we get energy from food, it is important for us to eat breakfast. Learners need to be able to recognise where energy is needed for living and other processes. Cleaning teeth, walking, running, reading, writing all need energy. Turning on lights and cooking food use energy. Warming our homes in winter or cooling our homes in summer uses energy. Drying clothes on the washing line. There are bicycles, motor cars, motor bikes and aeroplanes; all these kinds of transport need energy to move. It is up to the teacher to ask as many open-ended questions as possible to get learners to discuss the different uses of energy.
We need energy to carry out all our life processes. Do you remember learning about life processes in the beginning of the year?
Write down the 7 life processes that are carried out by all living organisms.
Feeding, growing, reproducing, breathing, excreting, sensing, moving
That is a very good question. Think about why you need to eat! We get our energy from the food we eat.
We eat plants and the food made from plants to give us energy. We also eat the meat from animals to give us energy.
But where does this energy in the food come from? Energy in our food comes from the Sun!
Energy from the Sun
Before going on with the rest of this chapter, let's identify some of the new words we will be learning about.
Word search
INSTRUCTIONS:
- Complete the wordsearch by finding the words listed below.
- Circle them with a coloured pen or pencil.
- Once you have found all the words, discuss with your partner what you think the word means to you.
Words to find:
food, energy, work, movement, Sun, energy, change, light, heat, absorb, reflect, transfer, chain
We get almost all of our energy on Earth from the Sun. We call this energy solar energy. Sol means Sun. Next term in Earth and Beyond, we will learn a lot more about the Sun!
The Sun is the closest star to Earth. A star is a giant ball of gas which releases energy. Some of this energy from the Sun travels to the Earth in rays. Some of the rays are light that we can see. Other rays like ultraviolet light and X-rays we cannot see.
When the rays reach the Earth, some reflect back into space. The Earth absorbs most of the solar energy. This heat warms the Earth and the air around it.
Use your dictionary to write down definitions for
absorb
To take something in, e.g. a sponge absorbs water, the earth absorbs heat.
Energy from the Sun causes heating
When light energy from the Sun hits objects, some of the energy is absorbed. Some of the energy bounces back.
MATERIALS (what you will need):
- 4thermometers
- black paper
- white paper
INSTRUCTIONS (what you must do):
Put one thermometer in a shady place.
Put three thermometers in a sunny place on the same surface.
Cover the bulb of one thermometer with black paper, cover the bulb of another thermometer with white paper, and leave the last thermometer in the Sun with no paper covering it.
Which thermometer do you think will show the highest temperature after 10 minutes?
Wait for ten minutes and then write down the temperature reading on each thermometer in the table.
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Thermometer |
Temperature (O°C) |
|
In shade |
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In the Sun with black paper |
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In the Sun with white paper |
|
|
In the Sun with no paper |
Which thermometer had the lowest temperature after 10 minutes?
The thermometer in the shade had the lowest temperature.
Did the thermometer in the Sun with the black or white paper covering have the highest temperature after 10 minutes?
The thermometer with the black paper covering had the highest temperature.
Explain your results.
The short answer: Black paper absorbs light so thermometer temperature is greater. White paper reflects light so thermometer gets less light. In the shade, thermometer is sheltered from the Sun, so less heat reaches thermometer so temperature will be less.
A longer explanation for these results: A thermometer measures the temperature of the air around its bulb. The more energy the air particles have, the higher the temperature will be. When we place a thermometer in the shade it is sheltered from the direct rays of the Sun. The air around the bulb will have less energy than the air around the thermometer which is in direct sunlight, and the temperature will be less.
The thermometer that has the black paper around it will have a higher temperature reading than the one with the white paper, because black paper will absorb more energy and make the air around the bulb hotter.
Without the Sun, the Earth would be a cold place with no life. Energy from the Sun has many different uses.
Light and warmth: We use the light from the Sun so that we can see during the day. We use the energy from the Sun to warm us.
Plants use light from the Sun to grow. Do you remember learning about what plants need to grow in the first term?
Animals eat plants to grow. The energy stored in the plants is used by the animals for life processes.
The transfer of energy from the Sun to plants to people is called an energy chain or food chain. It is a chain because each organism forms a link in the chain as energy is passed along from one organism to the next.
The arrows show the direction of the energy flow from one thing to the next. Look at the example of the food chain below.
Before reading or going through the next paragraph, or when you are explaining this concept to learners, first ask the question "What sort of energy does the Sun give off?" The answer is light and heat energy. You can then go on to explain how the light energy given off by the Sun is used by the grass to make food and the energy is transferred from one organism to the next in the food chain. This ensures that you do not restrict the learners' view that the Sun gives off both light and heat energy.
In this food chain, the Sun gives off light energy which is used by the grass to make food. The grasshopper eats the grass. The mouse then eats the grasshopper and the energy is transferred (moved) from the grasshopper to the mouse. Lastly, the owl eats the mouse.
Describing the transfer of energy from the Sun
INSTRUCTIONS:
- Look at the following food chain.
- In the space below, describe the transfer of energy from one organism to the next.
The Sun gives off light energy which is used by the plant to make food. The caterpillar eats the leaf to get energy to grow and move. The chameleon then eats the caterpillar.
- This food chain could be much longer! As more organisms eat the previous organisms, the food chain gets longer, and the Sun's energy is passed further along from one animal to the next. Look at the longer food chain below.
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In this food chain, what does the mongoose eat to get energy?
The snake
Trees are plants and so they get their energy from the Sun to grow. As it grows, the tree stores some of this energy in its wood. When we need heat and light at night and when it is cold, we burn the wood so that we can use the stored energy.
Long ago before dinosaurs lived on Earth, plants and animals also used the energy from the Sun to grow. Today some of these old dead plants and animals have turned into coal, oil and natural gas. Coal, oil and natural gas are called fossil fuels. We mine fossil fuels so that we can use the energy from the Sun that was stored millions of years ago.
When we use petrol or diesel to make cars or tractors go, we are really using stored energy which came from the Sun millions of years ago.
- We use energy for everything we do.
- We get our energy from our food.
- Energy in our food comes from the Sun.
- An energy chain or food chain is used to show the transfer of energy.
What is solar energy?
It is energy from the Sun.
Explain how animals get energy for life processes.
Firstly, the plants get energy from the Sun. The plants use the light energy to make food and grow. Animals then eat the plants or other animals that have eaten the plants in order to get their energy for their life processes.
Draw a food chain to show the flow of energy from the Sun to a
lion that has just eaten an impala.
Sun → grass and shrubs (plants) → impala → lion
List some fossil fuels.
Some fossil fuels are coal, natural gas, oil.
Where do fossil fuels come from?
Plants and animals from millions of years ago stored energy from the Sun. These plants and animals died and were buried over time. They have been under the ground for millions of years and have turned into fossil fuels
Draw and label a diagram to show where you get energy from when
you eat pap and when you eat wors.
pap: Sun → mealies → pap → person
wors: Sun → plants → cow → wors → person