Read all about it!  What is air?   When you have finished reading, click =CONTINUE=>.

It's hard to imagine that air is matter. Matter is something that has volume (takes up space) and weight. Air is invisible, it seems to have neither. For thousands of years, people didn't even know that air existed. But air does take up space, even if we can't see it. Air has weight, even if we can't feel it. We can observe that air has both volume and weight.

Just because we can't see air doesn't mean the space around us is empty. Like all substances, air is made up of atoms. Air has nitrogen and oxygen. Air also has carbon and hydrogen in it.

It is surprising that air even has weight. It is above our heads and all around us. Air exerts tremendous pressure, but we cannot feel it. We pay no attention to this pressure because we have always lived under these conditions. If air pressure were to suddenly disappear, we wouldn't survive its absence.

If we pay attention, we can see and hear signs of the air around us. We can feel air moving over our skin when we ride our bicycle quickly. We can also see it when we blow up balloons. Air is what we blow into the balloon.

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