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Any self-respecting teenage student will have got into trouble for dropping Mentos into a soda drink (and presumably the student will have had to clean up the resulting sticky mess of foamy liquid in the classroom). We will reproduce this timeless experiment safely and explain the science of the reaction.

First of all, this ‘reaction’ is better done outside. Open a two-litre (plastic) bottle of diet soda. The use of (warm) diet soda is recommended as it has been empirically shown to produce better results. An additional plus is that it is easier to clean as it contains artificial sweeteners instead of sugar.

Position the soda bottle on the ground. Roll an A4 paper into a tube with diameter the size of a Mentos. Load five Mentos into the paper tube covering the bottom of the tube with your finger. This paper tube allows you to drop the five Mentos in the diet soda at the same time. Position the tube directly over the bottle and pull your finger out of the way. All the five Mentos should fall in the bottle. Now run!

The thing that makes soda bubbly is invisible carbon dioxide (CO2), which is pumped into bottles at the bottling factory using lots of pressure. When you drop an object into a glass of soda, bubbles immediately form on the surface of the object. These are CO2 bubbles leaving the soda and attaching themselves to the object. This bubbling process is called nucleation, and the places where bubbles form are nucleation sites.

The reason why Mentos work so well is twofold – tiny pits on the surface of the mint and the weight of the Mentos itself. Each Mentos mint has thousands of tiny pits all over the surface. These act as nucleation sites, perfect places for CO2 bubbles to form. As soon as the Mentos hit the soda, bubbles form all over the surfaces of the candies and then quickly rise to the surface of the liquid. Mentos candies are heavy and quickly sink to the bottom. The gas released by the Mentos literally pushes all the liquid up and out of the bottle in an incredible and enjoyable soda blast.

For other fun experiments, visit www.stevespanglerscience.com/