How the Mentos Geyser Works – Theory Confirmed!

The Original Perfect Post Awards 07.08

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.

Read more about the Soda-Candy Explosions in the Chemical & Engineering News.

10 thoughts on “How the Mentos Geyser Works – Theory Confirmed!”

    1. No, because the flavored ones other than the mint one’s have a thick wax covering over it that gives it the flavor, it will work, but it would take twice the about of time to explode, so i recommend the mint ones.

  1. Hi Rebecca,

    The fruit flavored Mentos do work for the geyser and it makes a great science fair project to test the difference in height between the mint Mentos and the fruit Mentos. Happy Experimenting!

  2. My third grade son is working on an experiment using matter. It can involve any type of matter. We found the mentos/diet coke experiment and, of course, he thought it was so cool. We have researched this and have not found a reasonable theory behind the experiment. My question to you is, would this even qualify for an experiment on matter? Do you have a recommendation that would be better? He came up up with the theory that a Solid Matter (mentos) + a Liquid Matter (diet coke) = Gas (carbon dioxide). We have found many videos demonstrating the experiment, but not any on the scientific part of this. Can you give us more information on this? He has to give a presentation and demonstrate the experiment by himself in front of his class. Any information would surely help.

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