For this experiment, we warmed up coins (quarters are best because they are the largest of the easy-to-find coins). The children rubbed their hands back and forth over the coins while I discussed friction. When the coin was good and warm, they child (wearing thick gloves) pressed the coin onto the brick of dry ice.
SQEEEEE.
So what happened?
The dry ice under the coin rapidly sublimated which lifted the coin. The gas was released, and the coin fell back. This happened over and over producing a vibration and a sound.
This happened not only when we pressed the coins onto the dry ice but also when we used tongs to pick up small pieces. Each time we discussed why it happened--repetition is important.
This is a YouTube clip I found that shows what happens during this experiment.
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