Air show experiments
It's invisible, but it's everywhere. It's air, and you can make it do some amazing things! Try these experiments and find out more.
Heavyweight
What you'll need
- 30cm ruler
- Several sheets of paper. They can be newspapers.
- Table
How to do it...
Lay a 30cm ruler on the edge of a table so that about a third of the ruler extends over the edge. Place several large sheets of paper, such as newspaper pages, over the ruler. Hit the ruler sharply to try to make the paper fly into the air. It can't be done!
How does it work?
Air has weight. Because the paper is large, it has a lot of surface area for air to rest on. The air pushes down on the paper with such force that it's difficult to move it with the ruler. Pressure caused by the weight of the surrounding air is called atmospheric pressure.
Up in the air
What you'll need
A sheet of paper
How to do it...
Hold the edge of a sheet of paper under your lower lip. Blow hard over the paper. It should blow up, not down!
How does it work?
Fast-moving air blowing over the paper creates less pressure on the paper than the slower air that is under it. The greater pressure under the paper creates an upward force called lift. This illustrates Bernoulli's principle. It is the same force that keeps airplanes and birds in the air.
Bottles and balloons
What you'll need
How to do it...
Securely place deflated balloons over the tops of two empty drink bottles. Put the bottles in two plastic bowls or pails. Fill one container with hot water and one with ice cubes. The balloon on the bottle in hot water should begin to inflate.
How does it work?
The hot water heats the air in one bottle and the ice cools the air in the other. When air gets warm, it expands and rises, which inflates the balloon. Cool air contracts, causing the other balloon to shrink.
Bottled air
What you'll need
How to do it...
Show an empty drink bottle to a friend and announce that although the bottle may look empty, you can prove that it's actually full. Then put a deflated balloon into the bottle as shown, stretching the open end of the balloon over the mouth of the bottle. Can your friend blow up the balloon while it's inside the bottle? No way!
How does it work?
No matter how hard your friend blows, he or she won't be able to blow up the balloon while it is inside the bottle. This is because the bottle is already completely full – of air. Even though it's invisible, air takes up space.
Flutters
What you'll need
- Slip of paper 2.5cm wide and 7.6cm long
- Tape
- One-litre bottle
How to do it...
Cut a slip of paper about 2.5cm and 7.6cm long. Tape one end of the paper to a flat surface. Place a clear, empty one-litre bottle about 10cm in front of the paper. Then blow on the bottle, toward the paper. The paper flutters!
How does it work?
Moving air separates and travels around a curved surface. The air comes back together on the other side of the bottle and causes the paper to flutter.
The pressure is on
What you'll need
- Glass
- Piece of cardboard
- Water
- Sink or tub
How to do it...
Completely fill a glass with water. Place a piece of cardboard over the top of the glass. Then turn the glass upside down over a sink or tub, holding the cardboard tight against the rim of the glass. Now remove your hand. Ta-daaaa! The water should not spill out! (If it does, practice a few more times over a sink. Make sure there are no air bubbles inside the water glass.
How does it work?
The water stays in the glass because the pressure of the water inside the glass is less than the pressure of the air that pushes from the outside against the cardboard.
Paper racers
What you'll need
How to do it...
Get two sheets of paper of the same size. Crumple one sheet into a tight ball. Leave the other sheet flat. Hold the two pieces of paper above your head and let them go. The crumpled ball reaches the floor first.
How does it work?
Air resists the movement of objects, causing them to slow down. The flat sheet of paper has more surface area than the crumpled sheet, so there is more air resistance.
Text: Julie Vosburgh Agnone. Illustrations: David Bamundo.