Air is often an elusive thing for children, literally and figuratively. Children know that air exists, children know that you can breathe air, but how much space air takes up, or how heavy air is, that is more difficult to explain. And then you may still lack words. Because how do you make it clear in a simple way that air takes up space and has weight?
Our earth has an atmosphere. That atmosphere consists of air. We call the part in which we live of the atmosphere the Troposphere. That is the area of the weather change, where the clouds float and rain showers occur. This layer is about ten miles thick.
The closer you get to Earth, the closer the sky is. At sea level the air is heavier than high in the mountains. There the air is thinner and therefore weighs less.
Making visible that air takes up space
Necessities:
- A funnel
- An empty transparent bottle
- Wide masking tape or clay
- Water
How do you make it visible that air takes up space?
Place the bottle on the counter or on a table. Place the funnel in the opening of the bottle and tape it to the bottle with masking tape. Do this as carefully as possible, as there should be no more space between the bottle and the funnel. You can also do this with clay, because the intention is that it is properly sealed (airtight).
Now pour some water into the funnel and see what happens. If you have properly attached the funnel (airtight) to the bottle, you will see that no water gets into the bottle. It stays in the funnel.
How is that possible?
Because there was already air in the bottle, that bottle was already filled with air. Because you have attached the funnel airtight, the water cannot get into the bottle. The bottle is already full. It is full of air! If you now make a small hole in the bottle, the air can escape and water will enter the bottle. The water then takes the place of the air in the bottle.
Making visible that air has weight
In the previous experiment you saw that air takes up space and that where there is air, there cannot be anything else. Just think of a bicycle tire, it is also full of air.
How do I make it visible that air has weight?
Necessities:
- A ruler
- A clothes hanger
- Two balloons
- Adhesive tape
- A piece of string
- A balloon pump
Cut three strings. One long, and two shorter. Tie the long string on one end to the center of the ruler and the other end to the center of the coat hanger. Then tape the two other strings to the ends of the ruler with tape, and attach a balloon to each string. Then hang the coat hanger so that it can move freely and has all the space and see if the ruler is in balance. The ruler must hang straight (horizontally), that’s important!
Then release one balloon and inflate it with the balloon pump. Put a knot in it and reattach it to the ruler with the string. Now when you hang the hanger again, you will notice that the ruler is no longer hanging horizontally, and that the air-filled balloon is pulling the ruler down. You have now proven that air has weight too!
How is that possible?
Air has weight. At sea level, air weighs about 1 kg per square centimeter. That is only difficult to weigh with scales, because there is air everywhere. If you would place a container on a scale, you would only weigh the container, because there is just as much air in the container as next to it, above it, and below it.