Mentos in Coke experiment

Have you heard about the "Mentos in Coke" phenomenon?  It's a simple science experiment that your kids will go nuts for.  Try it out for yourself and teach your kids some simple science facts.

What you need:

• 1 x bottle of cola (diet cola works best)
• 1 x bottle of lemonade (or any other soda)
• 1 x packet of mint Mentos
• An outdoor area you can hose down afterwards

Number of players:
1

Activity:

It's an old trick: drop a Mentos into a bottle of Diet Coke and "whoosh" a sticky brown geyser shoots up out of the bottle.

To find out why it happens, you can explore a few variations:

• will it happen with any type of soda?
• does it only work with diet sodas?
• does it only work with white mint Mentos?

For the record, we tried it with both diet and full sugar sodas. It worked with both, but the diet soda produced a bigger reaction.

We tried it with cola and lemonade. Both worked.

We also tried it with coloured mentos and mint Mentos.  Again, both worked.

Why is it so?

There are many explanations for this phenomenon.  Here is one abridged version:

A bottle of soda is full of carbon dioxide (the bubbles.) The bubbles stay suspended in the liquid until the bottle is opened.

When you drop any sort of object into a bottle of soda, bubbles form on the surface of the object. This is called, "nucleation."

Add to this the fact that the surface of a Mentos is textured: it's made up of lots and lots of tiny craters. These tiny pits create a larger surface area and essentially provide many more "nucleation sites."

The Mentos drops to the bottom of the bottle, forming lots and lots of bubbles on its pitted surface along the way.  When all of this gas is released it forces the liquid up and out of the bottle in a giant whooshing geyser of sticky soda.

Why does it work better with diet sodas?

No one has worked out why.

But what they have worked out is: diet sodas are less sticky to clean up!

• Thanks to our sister company Kidspot Australia for creating the instructional video.