| Air is a kind of gas, but you can’t see it. Air is
everywhere. Things that are burning give off a gas called smoke.
Run in place very fast for a
minute. Do you notice how hard you are breathing? What you are
breathing is oxygen? You need oxygen to live. That's why you can
only hold your breath for a certain amount of time.
You can't see oxygen. It's
invisible. It is a gas. A gas is matter that has no shape or size of
its own. Gases have no color.
Gases
are all around you. You can feel gas when the wind blows. The wind
is moving air. Air is many gases mixed together.
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