Power of Air Pressure

Equipment Needed

Water
A gas or electric burner
A bottle with a screw-on lid

The Experiment

Pour half of a cup of water into the bottle. Leave the lid off.

Place the bottle on the burner.

As soon as you see steam coming from the bottle, remove it from the burner. (Use a potholder to avoid burning yourself.)

Screw the lid tightly onto the bottle.

As the bottle cool, you will see its sides beginning to show signs of strain.

By the time the bottle has cooled down completely, the sides will have buckled inwards

How it Works

When the water is boiled, steam and water vapor are created, forcing most of the air out of the bottle.

By screwing the lid onto the bottle when you removed it from the burner, you prevent air from returning to the bottle as it cools.

The steam trapped inside the bottle condenses into water, which lowers the pressure inside the bottle.

The greater pressure of the air outside the bottle causes the sides of the bottle to bend inward.