How Things Work: Mentos in Diet Coke

•SciTech Briefs
•How Things Work: Mentos in Diet Coke
Scientists have performed an experiment involving Mentos and Diet Coke that takes the legend out of “urban legend.” The experiment was first performed for David Letterman by school teacher Lee Marek in 1999.

The experiment involves something that you can do with soda that will not rot your teeth, unless you decide to drink Diet Coke combined with Mentos candy. Unlike Pop Rocks and soda — which don’t actually make your head explode if consumed together — combining Mentos with Diet Coke really does cause a chemical reaction.

The result of combining Mentos with Diet Coke, which has been showcased around the Web thanks to YouTube, is not the typical “fizz” that arises from opening a new bottle of soda. Drop a Mentos candy into a two-liter bottle of any diet soda, and the soda will erupt like a geyser that puts all sixth-grade vinegar and baking soda projects to shame.

More recently, the experiment has been made popular by the creators of the website, which contains numerous videos of the Coke-Mentos explosions. In particular, EepyBird shows videos of synchronized Diet Coke geysers, domino fountains, and even bloopers.

The Mentos and Diet Coke experiment has also received national attention. It was featured on an episode of Discovery Channel’s Mythbusters and on National Public Radio’s nightly news show All Things Considered.

The science behind this experiment goes deeper than the surface.

Water molecules are strongly attracted to one another and will collect around a bubble of carbon dioxide that is found in the soda, forming a sort of coating.

For more carbon dioxide bubbles to form, or for existing ones to grow larger, they must break the surface tension of the water molecules.

The theory with Mentos is that the gum arabic in the candy breaks the surface tension of these molecules, making the carbon dioxide bubbles form faster....