Red, White and Blue Geysers
A Patriotic new spin on the classic Mentos and soda reaction
It's our classic geyser experiment with a patriotic twist designed specially for the 4th of July. You've probably seen red, white, and blue sparklers or even fireworks the color of Old Glory, but we doubt you've ever seen colorful eruptions of soda like this.
- At least 3 rolls of Mentos
- At least 3 2-liter bottles of red, white and blue soda (or clear, lemon-lime soda)
- Geyser Tube or a piece of paper
- Red and blue food coloring or red and blue True Color Tablets (if you are using clear soda)
- To start, it's probably best to do this experiment in a park, yard, or other open area.
- Open three bottles of the clear, lemon-lime soda. Try not to spill any.
- Change the color of two of the sodas by placing 2-5 drops of red food coloring in one bottle and 2-5 drops of blue food coloring in another. Leave the third bottle clear. Alternatively, you can use our True Color Tablets. Our True Color Tablets don't stain like food coloring. Place 2 red (they look purple) tablets in one soda and place 2 blue tablets in another. Again, leave the third bottle clear.
- Unwrap 3 rolls of Mentos. The goal is to get all the Mentos into each bottle at the same time‚ so if you aren't using our Geyser Tube‚ you are going to need 2 friends to help you drop the Mentos into the other two bottles.
- If you are using a piece of paper, roll it into a tube just big enough to hold the loose Mentos. You'll want to be able to position the tube directly over the mouth of the bottle to drop all the candies in at the same time.
- Hope you remembered your running shoes… drop the Mentos in and run!
- There you have it, a patriotic red, white, and blue soda eruption.
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 explanations could be possible... and we welcome your thoughts.
As you probably know, soda pop 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. The pot of water will sometimes boil over because organic materials that leach out of the 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 carbon dioxide bubbles expand and release easily, creating a beautiful foam on top.
Though the red, white, and blue geyser uses clear, lemon-lime soda, generally the best geysers are made using diet Coke or diet Pepsi. 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 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 of some of our favorite eruptions on-line at www.SteveSpanglerScience.com.
On a personal note... I've performed this demonstration well over a thousand times - on television, on talk shows, at science conventions, for teacher associations, for CEO's at huge motivational speaking rallies, for Nobel Prize winners and for anyone else who might watch. 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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