What happens, if you throw a few Mentos candies in a bottle of coke? Well, you would probably get quite wet — those are the rumors. Are they true? There is only one way to find out: Try it!

With a device like the one shown on the left you can release the candies from a save distance. Here the tube containing the Mentos load is glued to a cap, which got a large hole so that the candies might fall into the bottle that special device is screwed on. A piece of wire can be used to hold the mentos back. When it is pulled out (with a wire from the distance) the Mentos drop and the fountain is released:

Wow! But we need more power! Reducing the diameter of the nozzle can help there, since less coke can pass it and a higher pressure will be build up. Let's see, if this theory is also true:

But kids! Don't try this at home...

... try it outside! :)

Now you ask how this can happen? Here is an explanation: A lot of carbon dioxide (CO2) is solved in the cola. On a rough surface it can start to form a bubble and the Mentos has such a surface. This is called a "seed" and you can see the same effect when pouring cola in a dirty glass. Furthermore the Mentos are quite heavy, so that they fall quite fast to the bottom of the bottle, striking a lot of cola in a short time. All those bubbles need space — and there is only one direction: through the bottleneck. Since the gas is still covered in a cola-bubble all the cola is carried along through the nozzle.