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What is air?

Posted by Isabel Becker-Spiegel
Grade level: K-3
School: California Distance Learning
City: Los Angeles State/Province: CA
Country: USA
Area of science: Earth Sciences

What is air?

Air is all around us, even at the top of the highest mountain and at the bottom of the deepest cave. We can't see it, but it's there!

Air is a mixture of different kinds of gasses. Anything you can hold in your hand, like dirt, or glass, or a book, is what we call matter. There are basically three types of matter: solids, liquids, and gasses. There are lots of differences between these three types of matter.

A big difference is temperature. If you heat a solid enough, it turns into a liquid. If you keep heating the liquid, it turns into a gas. For example, if you put an ice cube, which is solid, into a pan and heat it up, it melts. It turns into a liquid, in this case, water. Now keep heating the water, and it will turn into steam. Steam is a gas.

Air has lots of different gasses in it. The most important one is oxygen, which is what our body needs, and is what we get out of the air when we breathe. There are other gasses in the air too, but our body doesn't need them. Some gasses, like carbon dioxide, is "breathed" in by plants (they don't really breathe like we do though. They absorb air, like a paper towel absorbs a spill). They breathe out oxygen, which we breathe in. We depend on plants for the air we breathe!

The air surrounds the Earth like an orange peel surrounds an orange. It gets thinner as you get higher, so if you climb a mountain that's really high it gets hard to breathe. Eventually, the air completely thins out and there is nothing left. Astronauts, when they go up in the space shuttle, are up higher than the air and so they have to bring air with them. That's why they wear space suits when they go on space walks!

©2008 Phil Plait. All Rights Reserved.

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