1. UNIT 5
AIR AND
WATER
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2. Air
You cannot see air, but it takes up
space and it moves. Air is a mixture
of different gases. One of these
gases is oxygen. People, animals
and plants need oxygen to live.
7. Remember!
Air is a mixture of different gases.
One of these gases is oxygen.
8. Water in nature
People, animals and plants need water to live.
There is water in the sea, in rivers, in lakes and in
clouds.
Sea water is salty.
You cannot drink it.
You cannot water plants with it.
There is fresh water in rivers and lakes.
You can drink it.
You can water plants with it.
9. Changes in water
The water you drink is a liquid. You have to keep it in a
container like a bottle or a glass.
If you cool water in the freezer, it changes to ice. Ice is a
solid like a rock or a pencil.
If you heat water, it changes into water vapour. Water
vapour is a gas, like oxygen.
10. Match.
It is in the sea.
It is not salty.
Fresh Water You cannot drink it.
It is in rivers.
You can drink it.
Salt Water
11. Read the sentences.
1. Ice is a solid.
2. It is hot. The ice is changing into water.
This is a liquid.
3. It is very hot. The water is changing into
water vapour. This is a gas.
12. REMEMBER!
Water is liquid, but it can change into ice. Ice is
a solid. Water also changes into water vapour.
Water vapour is a gas.
13. Water pollution
People, animals and plants need clean water. You cannot
drink polluted water. Water is polluted when people put
rubbish and chemical products into rivers and lakes. There
is not much clean water in nature. Me must use it carefully.
14. Air pollution
Air can also be polluted. Air is polluted by smoke from
factories, traffic and heating systems.
