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.

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Comments (11)

  • Use A Repell-em Tablecloth For Your Outdoor Cookout! » Repell-em Blog Reply

    […] my kids had a big Mentos Geyser/ bonfire/cookout in the back yard. It was going to rain at any second, all through the party, so […]

    July 28, 2008 at 12:27 am
  •   Perfect Post, July 2008: Steve Spangler — Scheiss Weekly Reply

    […] am nominating Steve Spangler’s “How The Mentos Geyser Works” for a July Perfect Post […]

    August 3, 2008 at 10:30 am
  • Rebecca Baldwin Reply

    Do the fruit flavored Mentos work or do you just use the mint ones?

    March 15, 2009 at 4:59 pm
    • samantha Reply

      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.

      October 10, 2010 at 2:37 pm
  • Steve Reply

    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!

    March 16, 2009 at 1:15 pm
    • Lalalala Reply

      This is what I am doing for my big project this year. I will post my findings on here later.

      October 30, 2014 at 10:06 am
  • Deb Reply

    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.

    February 14, 2010 at 1:19 pm
  • juliegintzler Reply

    Hi Deb, for a full explanation on the science behind the mentos geyser, you can follow this link:
    Good Luck with your project!

    February 15, 2010 at 4:52 pm
  • maila Reply

    why does fresh soda explode when you put a mento in it

    April 19, 2010 at 11:04 pm
  • ben Reply

    why is it when you put a mento in a soda it explodes

    April 10, 2012 at 2:19 pm
  • mel Reply

    when my daughter did it, the fruit ones exploded more quickly and the guyser went higher

    May 1, 2012 at 2:55 pm

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