- To show that air has pressure
- Water glass
- Pieces of thin flat cardboard
- Fill the glass to the top with water.
- Place the cardboard over the glass.
- Holding cardboard tightly to the glass, carefully turn the glass upside down.
- Remove your hand from the cardboard.
- Hold cardboard in place against the glass.
- Tilt the glass or hold it sideways and the cardboard still remains in place.
- The water will leak out if the cardboard is not held tightly when turning the glass over.
- The cardboard sticks to the glass as it is turned.
- Did the water leak Out? Why? (The water leaked out because it was not held tight enough next to the cardboard.)
- What could you do to keep the cardboard dry longer? (Use thicker cardboard, answers will vary.)
- Did the cardboard stick when the glass was turned sideways? Why? (Yes, the pressure of the air next to the cardboard caused it to hold tight.)
- The air pressure kept the water from falling out of the cardboard covered glass.