Pick one before you read on. It is fine to be wrong.
By the end you can
Name energy stores, such as chemical, kinetic, elastic and thermal
Give an example of each store from daily life
Amina eats a banana. A little later she runs to the well and back. She is not tired at all. Where did her running come from?
Energy is what makes things happen. It makes things move, get hot, shine and make a sound. Nothing happens without it.
Energy is kept in places we call stores. A store is not a box. It is a way a thing holds energy, ready to use. We measure energy in joules, J. The next chapter uses them.
Draw it first
Draw three energy stores
1 Draw a candle. The wax is a chemical store. Energy waits in it until the candle burns.
2 Draw a ball with an arrow. A moving thing has energy in its kinetic store.
3 Draw a cup with steam. Hot things have energy in their thermal store.
Food and fuel are chemical stores. So are the wax of a candle, a battery and a bag of rice. They hold energy until something changes them.
The energy for Amina's run was in the banana. Her body moved it from a chemical store to a kinetic store.
A ball that is up on a roof has energy too, because it can fall. This is its gravitational store. A stretched rubber band has energy because it can spring back. This is its elastic store.
Neither thing is moving. Each holds energy, because of where it is or how it is stretched.
One more store is the thermal store. A hot thing holds energy in it. The hotter the thing is, the more it holds.
Light and sound are not stores. They are ways that energy moves from place to place. You will see this in the next chapter.
See it three ways
As a picture
In words
Every store has a name from what it is. Food and fuel hold chemical energy. Moving things hold kinetic energy. Raised things hold gravitational energy. Stretched things hold elastic energy. Hot things hold thermal energy.
Try it
Hunt for stores at home
You need: paper and a pencil, a walk round your home or yard.
Be safe: Look, do not touch, anything hot. Keep away from fires, stoves and hot pots.
Draw a table with two columns: "what I found" and "store".
Look for something that holds a chemical store. Write it in the table.
Find a moving thing, a raised thing, a stretched thing and a hot thing. Add each one to the table.
Write the name of the store next to each thing.
What you will see: Most homes have all five stores. Most of them do not look like they hold energy, because they sit still. Your list will be different from ours.
If you cannot try it, this is what happens.
A wrong idea many people have
A thing that is not moving has no energy.
Why it feels right: We see energy when something moves or burns, so a still thing seems to have none.
The test that breaks it: Hold a stone high over soft sand, then let go. It lands with a thud. Before you let go, it held energy in its gravitational store.
What is true: Stored energy cannot be seen. A still thing can hold a lot, such as food, a raised stone or a stretched band.
Key words
energy
what makes things move, heat up, shine and make sounds.
stores
a way a thing holds energy, ready to use.
chemical store
energy kept in food, fuel and batteries.
kinetic store
energy of a moving thing.
gravitational store
energy of a thing held up high.
elastic store
energy of a stretched or squashed thing.
Back to your guess
The answer is A: Yes. Energy is kept in the banana, ready for you to use.
Yes. Food keeps energy in it, in a store. Your body takes that energy out when you move, grow and stay warm. Things that are not moving can still hold energy.
Check yourself
Try each one before you look. A wrong answer tells you where to go next.
Which store holds the energy in a lump of coal that is not burning?
See the answer
Chemical store
Fuels such as coal, wood and gas hold chemical energy. It comes out when they burn.
If you chose A: Kinetic energy is for moving things. Coal sitting still is not moving. Go to S3.8.1.
If you chose C: Thermal energy is for hot things. Cold coal is not hot until it burns. Go to S3.8.1.
If you chose D: Elastic energy is for stretched or squashed things. Coal is neither. Go to S3.8.1.
Ravi pulls back a rubber band. Which store has the energy?
See the answer
Elastic store
A stretched band holds energy in its elastic store. When it springs back, that energy moves.
If you chose A: Gravitational energy is for things held up high. The band is stretched, not raised. Go to S3.8.1.
If you chose B: It is not moving yet. The energy waits in the stretch. It becomes kinetic only when you let go. Go to S3.8.1.
Which of these hold energy mainly in a chemical store?
See the answer
A bag of beans
Food holds energy in a chemical store. Your body takes it out when it digests the food.
If you chose B: The tea is hot, so it holds energy in its thermal store. It is not a fuel or a food in this question. Go to S3.8.1.
If you chose C: A rolling ball holds energy in its kinetic store, because it is moving. Go to S3.8.1.
A stone sits on a high shelf. Which store has the energy?
See the answer
Gravitational store
A thing held up high holds energy in its gravitational store, because it can fall.
If you chose A: It is not moving. Kinetic energy is for moving things. Go to S3.8.1.
If you chose C: A stone is not a food or a fuel. Its energy comes from being up high. Go to S3.8.1.
Tariq eats rice and then runs. In which stores is the energy, first and then later?
See the answer
Chemical store first, then kinetic store
Food is a chemical store. When the body moves, the energy goes into a kinetic store.
If you chose A: This is the wrong way round. The rice is a chemical store. Running makes a kinetic store. Go to S3.8.1.
If you chose B: The rice may be warm. But the energy for running was in the food, as a chemical store. Go to S3.8.1.
If you chose C: Rice is not held up high. The energy for running was in the rice, as a chemical store. Go to S3.8.1.
Which of these holds energy, even though it is not moving?
See the answer
The hot soup, in its thermal store
Hot things hold energy in a thermal store. The soup does not move, but it is hot.
If you chose A: Still things can hold a lot of energy. Hot soup, food and raised stones are all still. Go to S3.8.1.
If you chose B: The steam moves, but the soup itself is hot and holds more. Hot things hold thermal energy even when still. Go to S3.8.1.
Keep it
Copy this into your exercise book.
Energy is kept in stores: chemical (food, fuel), kinetic (moving), gravitational (raised), elastic (stretched) and thermal (hot). A still thing can hold energy.
Draw: A banana, an arrow, and a runner. Write chemical under the banana and kinetic under the runner.
