Mentos and Soda Project

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Setting Up a Mentos and Soda Fountain

This is the 'before' photo of the mentos and diet soda fountain.
This is the 'before' photo of the mentos and diet soda fountain. Eric is about to drop the roll of mentos candies into the open bottle of diet cola. Anne Helmenstine

This is a super-easy project that is safe and fun for kids. All you need are a roll of Mentos™ candies and a 2-liter bottle of soda. Diet cola seems to work best, but really any soda will work. One advantage of using diet soda is the end result won't be sticky.

Mentos & Soda Materials

  • roll of Mentos™ candies (any flavor)
  • 2-liter bottle of soda (diet soda is less sticky; diet cola seems to produce the best fountain)
  • index card or sheet of paper

Prepare for the Project

  1. This science project results in a jet of soda up to 20-feet in the air, so it's best if you set up outdoors.
  2. Roll a piece of cardboard or paper into a tube. Drop the roll of candies into this tube. In this photo, we used a sheet cardboard from the back of an old notebook. Use your finger to keep the candies from falling out.
  3. Open the bottle of soda and get ready...
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Doing the Mentos and Soda Fountain Project

The mentos & diet cola fountain is easy and fun.
This is an easy project. You'll get all wet, but as long as you use diet cola you won't get sticky. Just drop a roll of mentos all at once into a 2-liter bottle of diet cola. Anne Helmenstine

This part is really easy, but it happens fast. The fountain sprays as soon as you slide all of the mentos (at once) into an open bottle of soda.

How to Get the Best Fountain

  1. The trick is to make sure all of the candies drop at once into the bottle. Line up the tube containing the candies with the open bottle of soda.
  2. Eric just removed his finger and all of the candies fell. If you look closely at the photo, you can see a column of spray dropping from the tube in his hand.
  3. An alternative is to set a piece of paper or cardboard over the mouth of the bottle. Remove the card when you want the candies to fall.
  4. We used room temperature soda. Warm soda seems to fizz a little better than cold soda, plus it is less of a shock when it splashes all over you.
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Mentos and Soda Project - The Aftermath

This is the 'after' photo of the mentos & diet cola fountain.
This is the 'after' photo of the mentos & diet cola fountain. Notice how everyone scattered except Ry, now totally soaked?. Anne Helmenstine

Yes, you could clean up, but since you are wet, you may as well do the project again and again and again. Would you like to know what happened to cause the soda to spray? Before you open the soda, the carbon dioxide that makes it fizz is dissolved in the liquid. When you open the bottle, you release the pressure of bottling and some of that carbon dioxide comes out of solution, making your soda bubbly. The bubbles are free to rise, expand, and escape.

When you drop the Mentos candies into the bottle, a few different things happen at once. First, the candies are displacing the soda. The carbon dioxide gas naturally wants up and out, which is where it goes, taking some liquid along for the ride. The soda starts to dissolve the candies, putting gum arabic and gelatin into solution. These chemicals can lower the surface tension of the soda, making it easier for bubbles to expand and escape. Also, the surface of the candy becomes pitted, providing sites for bubbles to attach and grow. The reaction is similar to what happens when you add a scoop of ice cream to soda, except much more sudden and spectacular (and less tasty).