How the Mentos Geyser Works – Theory Confirmed!
It’s probably the most asked question we get… “How exactly does that experiment with the Mentos and Diet Coke really work?” From the outset (nearly eight years ago), we hypothesized that the exploding soda was a physical reaction, and the key factor in the release of carbon dioxide was the microscopic pits on the surface
of the chewy mint. However, there was no real scientific study that anyone could point to as the definitive answer… until now. In the June issue of the American Journal of Physics, Tonya S. Coffey, an assistant professor of physics and astronomy at Appalachian State University, in Boone, N.C., and her team of fearless physics students reported on the ingredients, temperature dependence, duration, and other parameters of the suddenly famous Mentos-Diet Coke reaction.
There has been considerable debate over gum arabic (found in the coating of the mint) and the role it plays in the physical reaction. Coffey’s group was able to confirm that the surfactant gum arabic is a key component of the reaction: It reduces surface tension, thereby allowing the soda’s carbon dioxide to make an especially rapid escape from the bottle.
The diet beverage’s aspartame and potassium benzoate provide a one-two punch to further reduce surface tension and ease bubble formation. This dynamic duo is more effective than sugar and creates a bigger explosion.