If you put 6 to 8 Mentos mint sweets into a bottle of Diet Cola at the same time, a lot of foam emerges in a very short space of time, which erupts into a geyser as it escapes the top of the bottle. With the right kind of bottle, a geyser of more than 4 metres high can be reached.
How does it work?
The cola is strongly saturated with carbon dioxide. With the addition of the Mentos sweets, the carbon dioxide is released from the liquid and foam is formed. The reason for the fast reaction rate lies in the shape of the sweets.
Viewed with the naked eye, the surfaces of the Mentos are very smooth. However under a microscope, it can be seen that the surface is in fact very rough. This is just like how the small scratches in a champagne glass cause bubbles of carbon dioxide to form; the many grooves in the sweets cause a large amount of gaseous carbon dioxide to emerge, leading to the intense foam that forms the geyser.
Safety Tips
A basin is built under the bottle. As Diet Cola comes without sugar, it is easier to squirt upwards.
