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STEM Activities

STEM Activity: Gusher

In this STEM activity, participants will learn the science behind the well-known Mentos® and soda pop experiment! Additionally, students will test the effectiveness of different types of soda and explore what variables produce the best reaction. 

Materials Needed

  • Coated candy mints (the Mentos® brand of mints produces the best results)
  • Goggles
  • Balloons
  • One two-liter bottle of clear diet soda pop
  • One two-liter bottle of clear sugared soda pop (same brand)
  • One two-liter bottle of diet cola
  • One two-liter bottle of sugared cola (same brand)
  • Paper funnels



  1. Set up the activity outside, at least 15 to 20 feet away from where the participants will be located. Once the mints are dropped into the soda pop bottle, the reaction is almost instantaneous and results in a large eruption.
  2. Shortly before the experiment, tape the paper funnels to the open soda pop bottles.


At-Home or In-Classroom Instructions

  1. Explain that like many inventions, the soda pop geyser came about by accident. In 2005, two men, one a lawyer and the other a juggler, were waiting for the juggler to go on stage at a show and passed the time by dropping their candy mints into a bottle of diet soda pop. Thus, an internet sensation began.

    This kind of accidental discovery can often lead to significant inventions. When Post-it® Notes were invented at the 3M Corporation®, they were intended to be sheets of paper with very strong glue. Since the glue sheets weren’t strong enough, the inventor, National Inventors Hall of Fame® (NIHF) Inductee Spencer Silver, put them away and forgot all about them. One day, another 3M employee, NIHF Inductee Art Fry, decided to use the weak glue sheets to mark all the songs in a song book he was going to use that night, and Post-it Notes were born! A number of accidental inventions like this have occurred throughout time and teach us an important lesson: always be curious!
  2. Explain that during today’s experiment, a parent or instructor will rapidly drop seven mints into one of the soda pop bottles. There is diet cola, regular cola, diet clear soda and regular clear soda. In this experiment, there is both a constant and two variables. The constant is the number of candy mints that will be dropped into each soda pop bottle (seven). The variables include the type of soda pop used (cola or other) and whether the soda pop is diet or regular (sugared). Explain that each time the experiment is conducted, participants will vote on which type of soda pop to use. Tell them that today’s experiment asks the question, “which combination of soda pop and mint candies will produce the highest soda pop fountain?”
  3. Place seven candy mints into the soda pop of your choice and move back rapidly. After the first fountain has erupted, ask the children to predict the reactions of the different types of soda.
  4. After adding the candy mints to each soda pop bottle, explain to the children that they have just seen that changing the variable in an experiment (in this case, the use of diet and then regular, sugared soda pop) can affect the experiment’s results. Some scientists believe that the sugar in soda pop slows down the reaction time of the candy mints dropped in the soda pop. Ask the children what they think is happening when the candy mints hit the soda pop.


What Are We Learning?

The water molecules found in soda pop are strongly attracted to each other, forming a very tight bond that links together the soda pop’s carbon dioxide bubbles. This is the gas that gives soda pop its bubbles and makes people burp. For carbon dioxide to form a new bubble or make a bubble bigger, the water molecules must push away from each other and break their surface tension, something they don’t want to do. When the mint candy is dropped into the soda pop, the candy’s materials cause the water molecules to break their surface tension. Also, the mint candies have a lot of very small pits in their surfaces called nucleation sites that attach to the carbon dioxide bubbles. The mint candies are also heavy and sink to the bottom of the soda pop, which just adds to the reaction. The combination of a heavy candy with a lot of carbon dioxide bubbles attached to it pushes the soda pop right out of the bottle, forming a gusher!

Looking for More STEM Activities?

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