Rocket powered pennies
Remember – heat causes things to expand (or get larger). Cold causes things to contract (or get smaller). Heating an object sealed inside another object can produce some interesting results. Let’s demonstrate with this experiment.
- Take an empty soda bottle and place it in the freezer for about 1 hour.
- Take the bottle out of the freezer. Wet the top and place a penny on the top so that it covers the mouth of the bottle (there should be no air leaks).
- Place the bottle back in the freezer for at least another hour.
- Take the bottle out of the freezer and grasp the sides with both hands. Hold the bottle tight and wait.
Were you surprised? Placing your hands around the outside of the bottle warms the air inside the bottle which then expands. Since the bottle is sealed by the penny, the heated air can only escape by breaking the ice around the rim and moving the penny. When the build up of heated air inside the bottle grows great enough, the ice gives and the penny pops off the bottle!