You will need:
- Glass bottle
- One piece of card board
What to do:
- Stretch the opening of the balloon over the rim of the bottle’s mouth. Make sure that the body of the balloon is inside the bottle.
- Try to blow up the balloon.
- The air in the bottle has nowhere to go and pushes on the balloon. This increases the pressure in the bottle when you try to blow up the balloon and you will not be able to blow it up.
- Pour water into the glass until it reaches the rim of the glass.
- Place the piece of card board on the glass. Hold it down so the card board covers the rim all the way around.
- Still holding the card board, move above a sink.
- Turn the glass upside down while still holding the card board. Then let go of the card board.
- Air pressure forces the card upwards, against the glass. The pressure is strong enough to stop the weight of the water pushing the card away.
You can watch a video for this experiment here: