Science Scoop

By Will Owen /// Staff Writer 

Ever wondered what the deal is with Coke and Mentos? So did I, then I found out and so will you!

Everyone knows it—even your Pep-Pep. You throw those Mentos right in the Coke and BAM you got yourself a foamy ‘splosion of Cokey Mento.

Why do you do that, Coke and Mento?

Maybe your mind brings you back to all of those baking soda-vinegar foam explosion volcanoes you saw in grade school.

But no!

The Coke-Mento phenomenon is actually something entirely different!

That familiar volcano reaction is what’s called an acid-base neutralization. That’s a chemical reaction between the acid (acetic acid) and the base (sodium bicarbonate). When those two meet, you make H2O and sodium acetate. Which blows up into a big ol’ ‘splosion.

On the other hand, when you take your Mento and you put it in your friend’s Coke as a prank, surprisingly, no chemical reaction takes place.

Instead, it’s a physical reaction (all the same molecules are present, just a change in their state).

The ultimate driving force for this reaction is the carbon dioxide that’s trapped in the Coca Cola. All that fizziness is begging to get out of the water, and it’ll do it any way it can. Thankfully, Mentos have lots of tiny micropores in their surface, which allows that CO2 to grab on and form bubbles—a process formally called nucleation by scientists. Ultimately, all those bubblies form rapidly, causing a massive release of gaseous CO2 exploding out everywhere! Go try it and see how much fun nucleation can be.

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