Easy Science – Make a Mentos® Geyser

400px-Diet_Coke_MentosAh, summer! What better time to make stuff erupt?

For this experiment, you will need:

  • one package of Mentos® candy
  • one 2L bottle of diet soft drink (best results are with cola)
  • one piece of construction paper approximately 8″ x 10″
  • tape
  • wooden toothpick

NOTE: This experiment should be performed outside and away from anything valuable or difficult to clean, as it makes a bit of a mess!

  1. Roll the construction paper around the unopened package of Mentos® so that it forms a long cylinder.
  2. Tape the ends of the cylinder, sticking the tape right around the tube of paper.  You can tape it in the middle, too, for added strength.
  3. Slide the Mentos® out of the paper tube, and insert one end of the tube into the open top of the 2L bottle of diet cola.
  4. With the toothpick, pierce the paper tube from one side to the other just above the mouth of the bottle.
  5. Drop 5 or 6 unwrapped Mentos® into the paper tube.  The toothpick should stop them falling directly into the liquid.
  6. Pull the toothpick out of the tube, stand back, and watch the geyser erupt!

Why It Works:

Soft drinks are essentially water, sweetener, and flavouring.  Each bottle then has a dollop of carbon dioxide forced into it under pressure, and is then tightly capped.  The carbon dioxide remains in suspension inside the water mixture until the pressure is released. When bottle is uncapped, for example, the carbon dioxide slowly fizzes away.  That’s why opened bottles of cola and other soft drinks eventually go flat.

Dropping the Mentos® into the liquid just speeds up the whole process.  The candies contain ingredients such as gelatin that disrupt the matrix of  water molecules in the soft drink, helping to suddenly and violently release the trapped carbon dioxide.  The carbon dioxide rapidly forms zillions of bubbles in the soft drink solution, which then force their way out of the bottle through the opening.

Enjoy your weekend!

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