Cool Science Experiment – Coca Cola and Mentos

We conducted a cool science experiment this week! Have you ever seen what happens when you mix Coke and Mentos? If you try it, stand back! You might get wet.

In this week’s activity, we experimented with dropping a package of Mentos candies into a 2 liter bottle of diet cola. Grammy and the boys took turns shaking the Mentos into the Coke.  Check out our video below to see who got the highest bubble fountain.

How Do You Perform This Cool Science Experiment?

You will need these supplies: unopened 2 liter bottle of soda, package of Mentos (contains about 14 candies), sleeve for dropping Mentos into soda, table, water hose for clean up.

Lay out your supplies on the table. Open Mentos and load them into the sleeve.

The sleeve can be a plastic tube just a little larger than the Mentos. Or you can make your own sleeve out of construction paper. I tried that, but the candies hung up in the rough paper tube. So, I made one from a plastic wrapper.

Open soda. Place one end of sleeve into the soda neck. Keep candy tube at an angle, so the Mentos don’t slip out until you are ready.

Once you are ready to go, straighten the sleeve and get it a couple of shakes. Then, step back! Soda will come shooting out the top of the bottle.

What is Happening in the Soda?

Carbonated drinks (soda) have carbon dioxide dissolved into the cola. This gas is what causes the bubbles when you drink it. When you sip your Coke, only a few bubbles form on the glass and the straw at a time.

However, when you drop Mentos into the soda, almost all of the gas comes out of solution at once. Bubbles tend to form on rough places on a surface. A drinking glass or an aluminum can both have smooth surfaces with few rough spots. But the outside of a Mentos is very rough with many uneven spots on which bubbles can form.

So, it’s all of these bubbles forming at once that cause the soda to shoot out the top of the bottle.

What Can Go Wrong?

This is a cool science experiment if you can get a tall geyser spewing out the top of the bottle. But that happens only if most of the Mentos are in the bottle when the bubbles start forming. If you drop just a few candies in, you lose the momentum and get only a small spurt.

So, find a smooth plastic canister or a slick sleeve so the candies will slide out easily.

What Kind of Soda Works Best?

Since Coke and Mentos create a dramatic effect, many people have studied how to maximize the soda spew. The following infographic is from Compound Interest and summarizes the relative heights achieved with different types of soda. Notice also the pictures illustrating the bubble formation in the soda.

The Secret of the Coke and Mentos Fountain

We conducted science experiments in Science Experiments for Kids – QWK Week 7, but this week’s experiment is the coolest!