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Mostly fill a glass jar with water. Add a little vinegar - 1/4 to 1/3 cup (60 ml) - and 2 tsp. (10 ml) of baking soda. Stir gently. Add a few raisins. As long as their surfaces stay fairly rough, they should begin to bounce up and down. This will also work quite well using clear soda water with the raisins. Alka Seltzer or clear soda will perform the same way. The irregular surfaces on the raisins hold some carbon dioxide bubbles.

When enough bubbles accumulate to lift the weight of the raisin, it rises to the surface. There, some of the bubbles of air escape into the atmosphere, and the raisin, which is denser than the water or soda, sinks to the bottom to start the cycle over again.

The effect will last longer if the container is sealed, as less carbon dioxide will be able to escape.