Make a geyser at home with diet coke and mentos. This super simple and fun science experiment will amaze your friends and family.

You Will Need:

  • Roll of mentos
  • 2 litre bottle of diet coke
  • Piece of paper
  • Playing card

This experiment should be carried out outside as it will make a mess!

The Experiment

  1. Open your bottle of diet coke
  2. Place the bottle upright on flat ground
  3. Unwrap the whole roll of mentos
  4. Roll the piece of paper into a tube just wide enough to load the mentos into
  5. Hold the tube upright and cover the bottom of the tube with the card
  6. Hold the tube and card directly on top of the bottle with the tube aligned with the mouth of the bottle
  7. Drop about half a pack of mentos into the tube, keeping the card in position directly over the mouth of the bottle and covering the bottom of the tube
  8. Pull the card out from under the tube, letting the mentos drop into the bottle
  9. Run out of the way and watch as the geyser erupts!
  10. Repeat the experiment with different fizzy drinks and different amounts of mentos to see which produces the largest eruption!

The Science

Why do the mentos and diet coke erupt?

Diet coke is fizzy and bubbly because it contains carbon dioxide gas. This carbon dioxide is waiting to escape the liquid in the form of bubbles.

When you drop something into a bottle of soda, this process is sped up. The surface tension is broken and the bubbles leave the soda and attach to the object. This process is called nucleation, and the places where the bubbles form are called nucleation sites.As you drop the mentos into the soda, bubbles form all over the surface. Mentos are covered in loads of tiny dimples which increase the surface area and create more nucleation sites where nucleation occurs as carbon dioxide in the drink forms bubbles.

Loads of nucleation sites means more nucleation and loads of bubbles as the carbon dioxide leaves the soda and attaches to the mentos. Nucleation occurs to such a large extent that the gas that escapes from the soda and onto the mentos increases the pressure and pushes the liquid up and out of the bottle into a massive geyser!

Want More Epic Experiments?
If you enjoyed this experiment and want to learn more about nucleation in greater detail, want more fun, more science, and more epic experiments, enrol now in our science holiday camps and spring term science classes where kids can learn, experiment, explore, and play!