Diet Coke & Mentos

Concept: Nucleation
Nucleation is a physical process in which a change of state occurs in a substance around certain focal points, known as nucleation sites. Nucleation sites assist the phase change of solids, liquids, and gasses. This is normally due to a greater surface to volume ratio or high surface area of the site. It usually happens in the early stage of phase change due to boiling, freezing, evaporation, or condensation. Common examples are the condensation of water vapor into droplets, the formation of ice crystals when water freezes, and the appearance of gas bubbles in a liquid.

Read Aloud: Mythbusters Science Fair Book by Samantha Margles

Ingredients:

      ·         20 oz. Diet Coke
      ·         3-5 Mentos
      ·         Construction Paper

      ·         Toothpicks

      ·         Tape

 Demonstration:

      ·         Wrap a sheet of construction paper around an unopened tube of Mentos and tape the seam. Remove the roll of Mentos from the paper tube.

      ·         Insert a toothpick into the tube about 1" from the bottom. Make sure the toothpick is centered and is stuck through the entire tube.

      ·         Place one end of the tube onto the mouth of a freshly opened bottle of Diet Coke. Secure the tube in place with more tape.

      ·         Drop 3-5 Mentos into the tube.
      ·         Pull the toothpick out of the tube and stand back!

Experiment:

·         What happens if you use another type of soda?

·         What happens if you use another type of candy?

Observations:
Although there are a few different theories about how this experiment works, the most likely reason is because of the combination of the carbon dioxide in the Diet Coke and the texture of the Mentos. The porous surface of the Mentos increases the surface area of the candy and creates nucleation sites. These nucleation sites allow carbon dioxide bubbles to rapidly form on the surface of the candy when dropped into the bottle of soda. Since the Mentos are heavy enough to sink, they react with the Diet Coke all the way to the bottom. Since Diet Coke is carbonated, there is a lot of carbon dioxide gas just waiting to escape the soda in the form of bubbles. When all this gas is released, it pushes the bubbling soda up and out of the bottle.