Dancing Dry Ice Bubbles by Bryce Hixson
Here's a density experiment that also demonstrates that different kinds of matter cannot occupy the same spice. Soap bubbles are blown into the air over an aquarium. They snake some hang time, but eventually gravity gets the best of them and the bubbles are pulled down into the aquarium. The funny thing is that they do not sink to the bottom of the aquarium, but instead, float and bounce above a layer of carbon dioxide.