Coke-a-Cola Eruption

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Coke-a-Cola Eruption


Every kid loves an explosion! Mine are no exception so following on from our elephant toothpaste experiment I wanted to see what else I could find. This experiment is great as it’s super simple, requires only 2 ingredients, is fun and also happens to be educational. This experiment is a great way to help kids understand the process of nucleation (yes, it is a real word).


  • 1.25L Diet Coke
  • 5 Mentos

We tried this experiment with ordinary Coke and the results were underwhelming. When I looked into it, this is a consistent theme for others who have also done this experiment.

The reaction relies on the amount of carbon dioxide that is contained in the drink, so I can only conclude that there is less carbon dioxide contained in ordinary Coke or that the sugar has some sort of impact on the separation of the carbon dioxide from the liquid. Either way, if you are looking for a bigger effect, go with the diet drink.


  1. Open the bottle of Diet Coke.
  2. Drop the mentos into the bottle all at once.
  3. Step back and watch the messy eruption!

The Science

I always assumed that this experiment involved a chemical reaction. It turns out that I was completely wrong. Nucleation is a physical reaction that occurs when gas is attracted away from a liquid and connects with another surface, in this case the mentos.

The bottle of Diet Coke contains a gas called carbon dioxide (CO2) which is what makes a fizzy drink fizzy. If you drop something into a bottle of fizzy drink, you will see small bubbles of CO2 clinging to the surface of the item that you have dropped in. This happens at the small dimples and ridges on the surface of an object which are called nucleation sites. Nucleation sites help the CO2 gas that is trapped to separate from the liquid. The mentos have thousands of tiny dimples in the surface which means there is thousands of nucleation sites for the gas to attach itself to. As the mentos sink to the bottom of the bottle they help free the CO2 more rapidly from the liquid than under normal circumstances. The reaction creates pressure which forces the liquid in the bottle up at the same time as the large quantity of gas that is trying to escape.

If you enjoyed this experiment, you may also enjoy our magic milk experiment which is another example of a physical reaction.

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