Air Around Us

1You cannot see air, but you can feel it

Take your exercise book. Hold it flat and fan it fast in front of your face.

Did you feel something cool push on your cheek? You did. But look hard at the space in front of your face. You see nothing there.

That thing you felt is air. Air has no colour. You cannot see it and you cannot hold it in your hand. But it is really there, and now you have felt it.

Try it again in two more ways:

• Blow gently on the back of your hand. That little push is air.
• Run fast across the yard. Feel the air on your face and your arms.

2Air is everywhere

Now think about Mugisha's bag again. It looked empty. He swung it through the air, and it became fat. The bag was catching something. It was catching air. Air was there all along, in the middle of the classroom, all around him.

Here is one more test you can do at home.

Take a bottle with nothing in it. Fill a basin with water. Now push the bottle down into the water, with the open top facing down.

What happens? Bubbles come rushing out of the bottle!

Think about that. Bubbles cannot come out of a bottle that has nothing inside. So the bottle was never really empty. It was full of air. When the water pushed in, the air had to come out, and it came out as bubbles.

Air fills the classroom. Air fills the bag. Air fills the bottle you called empty. Air fills the space between you and your friend. Air is everywhere around us.

3You breathe air

Put one hand flat on your chest. Breathe in slowly. Feel your chest grow bigger. Now breathe out. Feel it go down again.

Air goes in through your nose, and air comes out again. You do this all day. You even do it all night, while you are fast asleep.

Now try holding your breath. Count slowly: one, two, three, four... Soon your body shouts at you: I need air! And you breathe again.

You can live for hours without food. You can live for a while without water. But you cannot live for even a few minutes without air. Air matters that much.

Animals breathe too. The goat breathes. The dog breathes. The chicken breathes. Even the fish in Lake Kivu takes in air, but it takes its air out of the water. Plants take in air through their leaves.

Fresh air is good for you. Open the window in a stuffy room. Stay out of thick smoke. And when your family plants trees at umuganda, you are helping to keep the air good for everybody.

4Moving air is called wind

When air stands still, you hardly notice it. When air moves, you feel it at once. Moving air has a name: wind.

Wind can push things. You cannot see the push, but you can see what it pushes.

• Wind pushes the wet clothes on the line, so they flap and dry faster.
• Wind pushes dry leaves and dust along the road.
• Wind pushes a paper windmill so that it spins round and round.
• Wind pushes a boat with a sail on Lake Kivu, and the boat moves without a paddle.
• A strong wind can push a whole tree so that it bends over.

You can make a small wind yourself. Put a ball of paper on your desk. Now blow hard on it. It rolls away!

Your breath is moving air. Moving air is wind. And the wind pushed the paper. That is the whole idea in one little test.

Try it yourself

Think first, then tap Show answer to check.

Answer: air. The bag caught the air that was in the room.

Answer: the bottle was not really empty. It was full of air. The water pushed the air out, and the air came out as bubbles.

Answer: wind.

Answer: many answers are right. Clothes on the line, dry leaves, dust, a paper windmill, a sailing boat, the branches of a tree.

Answer: no. You breathe air all day and all night, even when you are asleep. Hold your breath and your body soon tells you so.