Coke and Mentos Science

We have all seen the millions of YouTube videos with various individuals performing this experiment. You get a bottle of coke and Mentos and simply drop them in. The result is a build-up of pressure and ultimate eruption of a plume of coke out of the bottle.

Funnily enough, the cause of the reaction had Scientists speculating for quite some time until Tonya Coffey and researchers in the US identified the primary factors resulting in the effect.

Surprisingly, the reaction is a physical one, rather than chemical. The addition of the Mentos leads to the rapid precipitation of carbon dioxide bubbles out of the solution. This process is called nucleation and happens due to the rough surface of the sweets. The ridges on the surfaces create sites on which the bubbles can grow and release by effecting the polar attractions between the water molecules.

The researchers also identified that the aspartame in diet drinks lowers the surface tension in the water and causes a bigger reaction, hence the reason diet coke works better than the original.

Interestingly, if you crush up Mentos and then add, the reaction is less impressive and the created fountain is lower. This is because full Mentos are heavier and drop to the bottom quicker. The resulting bubbles actually seed more bubbles as they rise through the solution… the result… a better plume of bubbles and a bigger fountain.

The ultimate DIY experiment… Let’s make a rocket!

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