Science Corner: Mentos + Soda = Geyser


If you’ve got a kid who loves asking questions about how the world works, pull up a seat. It’s time to talk science.

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At 3, The Big Explorer was content to look at bugs under a rock; these days he wants to bring them home and study them under the microscope. Where once he ooohed and ahhhed at photos of tornadoes and volcanoes in books, now he wants to understand why and how they happen.

Which is how the Mentos + Soda experiment wound up on our Summer Fun List. He was given a Mentos Geyser tube as a Christmas present and was finally ready to discover what it was all about.

What happens when you drop Mentos into soda?

A homemade geyser!


  • 2-liter bottle of diet soda (regular soda works too, but diet isn’t sticky)
  • A roll of Mentos candies
  • A Mentos Geyser tube (about $5) or a piece of rolled up paper
Reviewing the instructions


  • Find an open space outside with a flat surface – a large patch of lawn or driveway is perfect
  • Open the soda bottle & attach the geyser tube into the opening
  • Put the trigger pin in place to prevent the Mentos from falling into the soda too soon
  • Remove the top cap of the geyser tube & drop in seven Mentos
  • Replace the top cap of the geyser
  • With the drawstring attached to the trigger pin in hand, carefully step back from the soda (too fast & you might tip the soda over)
  • Start your countdown and …
  • Pull the trigger!

Carefully placing Mentos into the Geyser tube

Note: If you’re trying this experiment without the geyser tube, beware. The reaction is almost instant. Once you begin dropping the Mentos into the soda, prepare to get wet!

Just for kicks, we decided to try two different variations – one using regular Coke instead of diet, another using more than the recommended 7 Mentos.


  • When using mint Mentos & Diet Coke, the geyser rose up slightly above the roof line of our house
  • When using fruit flavored Mentos & regular Coke, the geyser rose just even with the roof of our house
  • When using more than the suggested 7 Mentos, there was no geyser at all!

What causes the reaction? You can get a full explanation here, but if your kid is anything like The Big Explorer, simple is a good place to start: A massive release of gas pressure. Yeah, you know you want to laugh, too.

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  1. says

    This is such a fun experiment… in fact, this was our big Memorial Day Weekend family fun project! 🙂 Our neighbors across the street even pulled up a seat to watch!

  2. says

    I've seen this posted several places and thought "I should do that." Well, I better get on it before it gets too cold 😉 Thanks for the reminder!

  3. says

    Ooooh, a science-themed party sounds fun! Yeah, no way you can keep kids from wanting to get soaked. The whole show is just so exciting.

  4. says

    Fun! We just went to a Science themed birthday party a few weeks ago and this was one of the experiments. It was a big hit. Of course, many of the boys also decided to stand near the geyser and got soaked and sticky. Good to know about the results when varying the procedure.

  5. says

    Heck yes! I love this! My friends and I used to do this all of the time growing up. Makes me want to make a trip to the store to relive the awesomeness again! 🙂