The Infamous Coke and Mentos Experiment

The science experiments my children talk about for months afterwards are generally the messy ones, like our splatter patterns, glow in the dark oobleck, baking soda experiments and the well known coke and mento experiment.

If you try this classic chemis t ry experiment definitely do it outside as it's VERY messy and sticky. Sometimes you'll see it called a coke and mento geyser, as the eruption looks like a geyser!

Coke and Mentos Experiment

You'll need:

Coke or other fizzy soda

Mentos

Instructions

We dropped two Mentos into a bottle of normal Cola and Diet Cola. I used the cheapest brands available in our local supermarket.

Diet coke and normal coke for a coke and mento geyser eruption

Once you drop the Mentos into the coke, stand back as it's VERY explosive. The trick is to drop the mento in as fast as you can. If too much of the fizz escapes before you add the mento the reaction won't be as good.

What happens when Coke and Mentos mix?

There are several theories, but it's thought that the many small pores on the surface of the mento speed up the release of carbon dioxide (CO₂) gas from the soda as they give a larger surface area for the reaction to occur over, causing foam to erupt at a super fast rate.

Which soda works best with Mentos?

Any fizzy drink will produce a similar effect, but diet drinks seem to work best, as we found in our investigation. This is most likely due to the particular chemicals in diet drinks.

The reaction isn't a chemical reaction but a physical reaction! The molecules haven't been chemically changed, just re-arranged!

See Steve Spangler for a much more thorough explanation of this very cool experiment.

Does the number of mentos affect the height?

More Mentos candies should mean a better explosion, but there is a limit to how many will actually make a difference. We found 7 to be the maximum number we could drop in at once.

More Coke and Mentos Eruption Ideas

Investigate to find out if the type of fizzy drink matters. Does diet soda make a taller geyser?

Try lots of different sodas and diet sodas.

Test fruit-flavoured Mentos instead of mint flavoured.

Find out if the number of mentos affects the height of the geyser.

Investigate to discover what would happen if you left the top off the Cola for a few minutes before adding the Mento.

Use the reaction to power something? Maybe a LEGO car?

Design a device to drop several mentos into the bottle at the same time. Can you find out what the optimum number of mentos for a 2-litre bottle of soda is?