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Is Air Really Something?

What you’ll find out

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No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.

Air takes up space

You cannot see air, so it is easy to think it is nothing. Try this. Push a dry paper towel into the bottom of a cup. Turn the cup upside down. Push it straight down into a bowl of water. Now lift it out. The towel is still dry! The cup was already full of air, so the water could not get in. Tilt the cup under the water and a big bubble comes out. Then the water rushes in. Air takes up space. That means it is matter.

Air has weight, and tiny pieces

Air has weight too. Hang two empty balloons from a stick that balances on a string. Blow one up and hang it back. The side with the full balloon dips down. The air inside it weighs something! All the air in a classroom weighs more than several grown-ups. So why can you not see it? Air is made of tiny pieces called particles. They are far too small to see, with lots of empty space between them. That is why air can be squeezed. Push on a sealed syringe full of air and it squashes. Let go and it springs back.

Curriculum links: NGSS 5-PS1-1