What is air?

How long can you hold your breath? Maybe 20 seconds or even 30? If you were a seal, you could hold your breath for up to 30 minutes. But sooner or later, every person and every seal has to come up for air. We need air to live. We can’t see it. We can’t touch, smell or taste it. But we can feel it moving, or feel ourselves moving through it, for example when riding a bicycle. We are surrounded by air everywhere on Earth. And that’s a good thing, because air contains a gas we urgently need. It’s called oxygen. If we don’t get oxygen, we die within minutes. Of every 100 parts of air, about 21 are oxygen. Another 78 parts are nitrogen. The rest consists of water vapor, carbon dioxide, argon and other gases that are present in the air only in very small amounts. We call the tiny particles that make up air molecules. These molecules move around. For example, when the sun warms them, they move faster. Then they need more space and rise up. When they cool down, they move less and sink back to the ground. So warm air rises and cold air sinks. As it does, it flows into the space left behind by the rising warm air. We call the movement of air wind. Wind can, for example, push clouds along. - Photos: Hamsterkiste