... or do they pop from the side or is it random? A soap bubble consists of a thin layer of water trapped between two layers of soap molecules. The liquid layer is thin, but it is still affected by gravity, so as a bubble floats, the water is drawn to its base. The film at the top of the bubble thins, even as evaporation removes liquid from the entire surface, until finally the bubble pops -- from the top. If you freeze bubbles with dry ice, you can pick a bubble up to examine it more closely to verify this for yourself. Another fun way to view bubbles is to color them.