Recommended Grades: All ages

By now, we have all heard about, or maybe even tried, the Mento and Diet Coke soda geyser experiment. If you haven’t tried it yet, it is explosive fun and sure to be one of your kids’ favorites! And of course, against all your protests, they will want to do it again and again.

So, what are we learning from this experiment other than how to clean up a big sticky mess? Here is the big takeaway from the experiment. The reaction taking place here is a physical reaction! Which means that the pieces of the reaction, mainly dissolve carbon dioxide gas, are already there! Compare this to a chemical reaction (such as baking soda and vinegar) in which reactants are converted to one or more different substances.

While a soda is in an unopened container, the carbon dioxide gas is kept in solution. When you open the soda, some gas escapes. The escaping gas forms bubbles and foam although most stays trapped by the surface tension of the liquid. So why do the Mentos cause such an explosive reaction? If you looked at a Mentos candy under a microscope, you would see that the smooth surface is full of scratches and dents. These scratches and dents increase the surface area of the candy which the carbon dioxide gas attaches to. This accelerates breaking the carbon dioxide molecules bond with the water in your soda and results in the carbon dioxide gas rapidly trying to escape the bottle!

Ready to give it a try?

Material:

• Mentos mint candy (1 pack)
• 2-liter Diet Coke
• Some sort of funnel, which can be made from rolled up paper

If you haven’t tried this experiment yet, the setup is pretty easy.

1. Start by making a tube to use for a funnel. You can do this by wrapping paper around the pack of Mentos and taping the end to hold this shape.
2. Use a small piece of paper to cap one end of the tube.
3. Open the pack of Mentos and place all of them in the tube.
4. Place the bottle of Diet Coke on a flat area outside where it is okay to get a little messy.
5. Slowly open the new bottle of Diet Coke.
6. Place the tube of Mentos over the opening of the soda bottle.
7. Remove the piece of paper holding the Mentos in the tube, allowing the candies to drop into the soda all at once. Quickly get out of the way!

More science!!!

Did you know, if you could shrink the Earth to the size of about a billiard ball it would be just as smooth (if not smoother)! Similarly, if we looked at the Mentos under a microscope, we would see lots of scratches and dents. Scientists refer to this as a difference in scale.