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Homemade Geyser Tube

Create your own launching mechanism for the famous Mentos and diet soda reaction and eruption.

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We've been performing the Mentos Soda Geyser here at Steve Spangler Science for years. We've launched so many geysers, in fact, that we created a tool to help streamline the process of creating the eruption. While the Geyser Tube is, hands-down, the best way to create a soda geyser that can be 30 feet tall, you might not be able to get your hands on one right away. So we're going to teach you how to create a Homemade Geyser Tube with stuff you have at home.

Materials
  • Diet soda
  • MENTOS® candies
  • Construction paper
  • Tape
  • Toothpick

Videos

  • Homemade Geyser Tube - Sick Science #145
Print Experiment

Experiment

  1. Roll construction paper around an unopened roll of Mentos candies.
  2. Use tape (electrical or duct) to hold the shape and size of the rolled paper Use tape at both ends, wrapped around the paper tube's entire circumference, and remove the roll of Mentos. 
  3. Place one end of the paper tube into the mouth of a freshly-opened, 2-liter bottle of diet soda. Secure the tube in place with a bit of tape.
  4. Just above the the mouth of the bottle, insert a toothpick into the tube. Make sure the toothpick is centered and is stuck through the entire tube.
  5. Drop 5-7 Mentos into the top of the tube.
  6. When you're ready (and preferably in an open outdoor area), yank the toothpick out of the tube and stand back!

Take It Further!

If you want to take your Geyser-ology to the next level, you need the best eruption-making tool on the market... Steve Spangler's Geyser Tube!

Recent improvements to the Geyser Tube have taken the geyser-creating tool to a whole new level. The trigger mechanism now has a double pull pin action, making sure there's no unwanted eruptions. When you're ready to pull the pin, a tighter seal means that you can achieve a 30 foot geyser with as few as two MENTOS® candies.

How Does It Work?

Here's the question of the day... Why do Mentos mixed with soda produce this incredible eruption? You should know that there is considerable debate over how and why this works. While we offer the most probable explanations below, we also understand and admit that other explanation could be possible... and we welcome your thoughts.

As you probably know, soda is basically sugar (or diet sweetener), flavoring, water and preservatives. The thing that makes soda bubbly is invisible carbon dioxide gas, which is pumped into bottles at the bottling factory using tons of pressure. Until you open the bottle and pour a glass of soda, the gas mostly stays suspended in the liquid and cannot expand to form more bubbles, which gases naturally do.

But there's more... If you shake the bottle and then open it, the gas is released from the protective hold of the water molecules and escapes with a whoosh, taking some of the soda along with it. What other ways can you cause the gas to escape? Just drop something into a glass of soda and notice how bubbles immediately form on the surface of the object. For example, adding salt to soda causes it to foam up because thousands of little bubbles form on the surface of each grain of salt. Many scientists, including Lee Marek, claim that the Mentos phenomenon is a physical reaction, not a chemical one.

Water molecules strongly attract each other, linking together to form a tight mesh around each bubble of carbon dioxide gas in the soda. In order to form a new bubble, or even to expand a bubble that has already formed, water molecules must push away from each other. It takes extra energy to break this "surface tension." In other words, water "resists" the expansion of bubbles in the soda.

When you drop the Mentos into the soda, the gelatin and gum arabic from the dissolving candy break the surface tension. This disrupts the water mesh, so that it takes less work to expand and form new bubbles. Each Mentos candy has thousands of tiny pits all over the surface. These tiny pits are called nucleation sites - perfect places for carbon dioxide bubbles to form. As soon as the Mentos hit the soda, bubbles form all over the surface of the candy.

Couple this with the fact that the Mentos candies are heavy and sink to the bottom of the bottle and you've got a double-whammy. When all this gas is released, it literally pushes all of the liquid up and out of the bottle in an incredible soda blast. You can see a similar effect when cooking potatoes or pasta are lowered into a pot of boiling water. The water will sometimes boil over because organic materials that leach out of the cooking potatoes or pasta disrupt the tight mesh of water molecules at the surface of the water, making it easier for bubbles and foam to form.

When a scoop of ice cream is added to root beer, the float foams over for essentially the same reason. The surface tension of the root beer is lowered by gums and proteins from the melting ice cream, and the CO2 bubbles expand and release easily, creating a beautiful foam on top Next question... Why should you use diet Coke or diet Pepsi? The simple answer is that diet soda just works better than regular soda. Some people speculate that it has something to do with the artificial sweetener, but the verdict is still out. More importantly, diet soda does not leave a sticky mess to have to clean up. Hey, that's important!

What's the record for the biggest Mentos fountain? My official record is a 18 foot blast that shot up and almost took out a half million dollar, high-definition television camera. You'll find video on-line at www.SteveSpanglerScience.com of some of our favorite eruptions.

On a personal note... Steve has performed this demonstration well over a thousand times - on television, talk shows, science conventions, teacher associations, for CEO's at huge motivational speaking rallies, for Nobel Prize winners and anyone else who might watch. And the reaction is always the same... that's amazing! My thanks to Lee Marek who originally shared the Mentos idea with me and to the hundreds of teachers and science enthusiasts who continue to share their funny pictures, videos and experiences.

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