A physical reaction where candy mint mentos are dropped into diet soda. The sugar coatings on the mints acts like a perfect nucleation site for the dissolved carbon dioxide in the soda to turn into bubbles. The result is that the majority of the carbon dioxide changes from liquid to gas form in just a few seconds. This sudden change of phase causes a plume of soda to be ejected from the bottle at great force, causing the soda to make a fountain two meters high.