Mentos and Soda Geyser

SODA AND MENTOS GEYSER: Anticipation of a geyser is as exciting as watching the geyser itself! Putting Mentos candy into a bottle of diet cola creates an amazing liquid geyser. The carbon dioxide bubbles in the soda attach themselves to thousands of tiny surface pits in the Mentos candy. The bubbles become numerous, creating gas and rapidly pushing the liquid out of the bottle. The effect is intensified because the heavy Mentos candies sink in the bottle, increasing the number of bubbles produced.

STOP LICKING THE TABLE! The excitement and anticipation of seeing a geyser of soda pop is a delight for children and adults. Inevitably, some of the students will see it as a waste of sweet drink and minty candy. I recommend quickly gathering the spent soda bot- tles so children don’t grab and attempt to drink the leftover soda and Mentos. Even with the bottles removed, there are students who will go as far as to lick the soda right off the launch pad (usually an outdoor table or bench). If I preface the experiment with the “no licking the launch pad” rule, it only seems to plant the idea. This remains an ongoing concern; you can temper this behavior with the mention of bird droppings on outdoor surfaces.

MATERIALS: 2-liter bottle of diet cola (we use sugar free cola because it is not as sticky) * Mint flavored Mentos candy (at least 7) * Quick release geyser tube

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HOW TO: 1. Open your bottle and place it on the ground or on a surface outdoors. 2. Put at least seven Mentos candies into your tube. 3. Drop the Mentos into the bottle of cola. Do this quickly (the reaction is instant). 4. Stand back and enjoy the geyser.

How to have your group make it: 1. Make sure that everyone gets a turn putting Mentos into the tube. With a larger group, we will do multiple bottles, changing the number of Mentos for each bottle and comparing geyser heights. This way all students get an equal chance to put Mentos in the tube. 2. Have students stand back away from the geyser as it can go as high as 20 feet.

THE LESSON: Soda pop is full of carbon dioxide gas. The Mentos candy provides a place for the dissolved carbon dioxide to “escape” from the liquid. This process is called nucleation. There are so many little holes on the Mentos (so many places for bubbles to gather) that the escaping gas creates a powerful “geyser.”

PRESCHOOL SCIENCE VERSION: outdoors, 15-20 minutes This is a thrilling demonstration for younger children. Everyone participates by putting a Mentos candy in the tube and witnessing the geyser. Give the explanation, mount the tube on the bottle, have children take turns putting Mentos in the tube, stand a safe distant back and start the geyser!

VOCABULARY: Physical reaction, nucleation, nucleation site, carbon dioxide, geyser