Fizzy Fountain

What you need:

  • soft drink, eg. diet coke
  • mentos

What to do:

  1. Open the soft drink bottle and place it in a tray – this will get messy. Listen closely when you open the bottle. You will hear a hiss.
  2. Drop about half a pack of mentos into the soft drink.
  3. Stand back and watch your fizzy fountain.

What happens:

The surface of the mentos are covered in tiny craters. This provides a very large surface area. Soft drink is full of a gas called carbon dioxide (CO2). This is what makes it fizzy and what causes the hiss you hear when you open the soft drink bottle. This gas forms bubbles on the surface of the mentos (this is called nucleation), but because there are the little craters, lots of carbon dioxide is released. This causes the soft drink to rush up and out of the bottle. You can continue adding mentos again and again, until this reaction stops and all the carbon dioxide is released.

You can experiment with different variations of this experiment. Try different soft drinks. Try different flavours of mentos. What does the soft drink taste like after no more fizzing happens?

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