About one-fifth of the air is oxygen.
Human beings and other animals would not be able to survive without oxygen.
When we breathe, our lungs take the oxygen we need from the air.
Another very important gas in the air is carbon dioxide.
When we breathe out, we release carbon dioxide into the air.
In daylight, plants take in the carbon dioxide they need to live and grow, and they make oxygen.
They then release the oxygen back into the air.
About four-fifths of the air is nitrogen.
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We breathe in nitrogen, but we don’t use it.
There are also small amounts of other gases in the air. Argon is one of these.
We breathe in argon but, like nitrogen, we don’t use it.
The air also contains tiny amounts of water vapor.
Green plants take in carbon dioxide from the air. Plants use carbon dioxide and water to make glucose, a type of sugar used for food energy. In the process, plants give out oxygen through their leaves.
It isn’t just living things that use the oxygen in the air. A flame needs oxygen to burn. There’s no oxygen in outer space, so you can’t light a match there.
Oxygen mixes with other substances too, and it sometimes changes them. Oxygen and water make iron turn to rust. As the iron rusts, it uses up oxygen in the air.
Can we see air?
If you go out on a windy day, you can feel the wind tugging at your body, hair, and clothes.
You can see the trees and flowers bending and the clouds racing across the sky.
Perhaps an old newspaper is blown along the road, or the smoke from a chimney is blowing out sideways instead of going straight up.
What is doing all this pushing and shoving?
What is moving everything about?
It is air.