We tried an experiment from 365 More Simple Science Experiments with Everyday Materials. The idea is that if you put a bottle in the freezer, it fills with cold air. When you take the bottle out of the freezer, the air inside the bottle warms up and therefore expands. If you block the way out for the expanded air, it will cause pressure to build up behind the blockage.
We first tried with a plastic bottle, putting it in the freezer for 5 minutes. We took it out, put a wet quarter over the bottle opening, and waited. Unfortunately nothing happened. We tried a glass bottle with a smaller opening, thinking the quarter wasn't fully blocking the mouth (or that the sound of a quarter on plastic wasn't very noticeable). The quarter did lift up and clank back down as pressure built up and was released in the warming bottle . However, there was a long time between clanks. We tried cooling the bottle overnight to make sure the air inside was very condensed. This worked well. We got lots of clanking, one after the other. Jr. scientist A. got quite a kick out of it.
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