- 2 liter plastic soda bottle
- small coin
Be sure the coin is big enough to fit over the opening of the
bottle. Wet the coin with water before placing it on the 2-liter
bottle. The water will enable a good seal around the top. Place both
hands around the sides of the 2-liter bottle without squeezing the
The warmth from the hands will warm the air inside the bottle.
When the air inside warms, the air will expand causing the coin to
flip up to release the build up. This demonstrates that hot air
expands its molecules causing them to become more active and less
dense than the colder air.