This demo illustrates the presence of atmospheric air pressure and shows how the force that it exerts is greater than the force of gravity in some situations.
Wear appropriate PPE: safety goggles.
- Fill the glass with water right up to the brim.
- Place the index card on top of glass and hold it firmly in place.
Students engage in Think, Pair, Share (see Teaching Suggestions/Hints):
- Think: What will happen when the glass is held upside down and the index card is no longer held in place?
- Pair: Discuss the question with a partner.
- Share: Hold a brief class discussion on the prediction.
Ask students to justify their predictions using their existing knowledge.
Lift the water-filled glass over the tray with one hand, holding the index card to the mouth of the glass with the other hand. Carefully turn the glass upside down. Release the card.
Ask students to explain their observations.