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Saturday, Nov. 29, 2014

Mentos plus Diet Coke provides a geyser-full of fun

Tuesday, June 27, 2006

(Photo)
Sarah Plath discovers the hard way what it takes to become a Sentinel intern as she holds onto a spewing liter of pop.
(Sentinel photo by Beverly Van Buskirk)
What do you get when you mix Mentos mint candies with Diet Coke?

a) a science experiment gone awry;

b) a spewing mess; or

c) another potentially life-threatening endeavor for our ever-intrepid Sentinel interns.

Yes, gentle readers, if you answered all of the above, you would be correct.

In the past few months, hundreds of amateur videos have been flooding the Internet, all showing the results of the same oddball phenomenon: If you drop the quarter-size Mentos candy into a liter of Diet Coke, prepare yourself for a geyser-full of soda with sugary spurts that can go as high as 20 feet into the air.

"It's a funny thing to do," Sidney Shapiro told to the Wall Street Journal recently.

Shapiro, a 26-year-old student in Israel, posted video of his Mentos-Diet Coke experiment on Google Video in May.

The popularity of Shapiro's video, and the approximately 800 other videos that followed, has produced a gusher of free publicity for the manufacturer of Mentos.

"We're tickled pink by it," remarked Pete Healy, the U.S. division vice president of marketing for Perfetti Van Melle, the Italian company that makes Mentos.

So what makes Mentos and Diet Coke such a combustible combo? Well, that's a question which is open to some debate.

For the purposes of our experiment, writer Don McDowell slowly unwrapped a roll of Mentos while intern Sarah Plath carefully opened a bottle of soda.

Our goal was to drop all of the Mentos into the soda at the same time. As it turned out, Don was only able to place 2-3 of the mint candies into the pop before the soda spewed out of the container.

Soda pop is, of course, basically sugar (or dietary sweetener), water, and preservatives. What makes pop bubbly is the invisible carbon dioxide gas that's pumped into bottles at bottling facilities.

Until you actually open the bottle and pour yourself a glass, the gas pretty much stays suspended in the soda and cannot form more bubbles.

But if you shake the bottle before you open it, the gases are released from the protective hold of the water molecules. It'll escape with a whoosh, taking some of the pop with it.

So does that mean the Mentos phenomenon is strictly a chemical reaction? Is it like when you jiggle a can of pop before you open it?

Well, maybe yes.

But maybe no.

Many scientists argue that when the Mentos meet the Diet Coke, it's a physical reaction that allows the two to interact.

Water molecules strongly attract one another. Together, they link to form a tight little mesh around each bubble of carbon dioxide gas in the soda. So in order to form a new bubble that has already formed, water molecules must push away from each other. It takes extra energy to break that surface tension and the water acts as a resistance to the expansion of bubbles in the soda.

When you drop the Mentos into the soda pop, the gelatin and gum arabic from the dissolving candy breaks the surface tension. This disrupts the water mesh, so that it takes less work to expand and form new bubbles.

Each of the Mentos candies has thousands of tiny "pits" all over its surface. These tiny pits are called nucleation sites. They're the prefect place for carbon dioxide bubbles to form. As soon as the Mentos hits 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, you've got yourself a double-whammy. When all this gas is released, it literally pushes all of the liquid out of the bottle in an incredible soda blast.

Ever have a root beer float? Once ice cream is added to the root beer, the "float" foams over the glass for essentially the same reason. The surface tension of the root beer is lowered by gums and proteins from the melting ice cream, the bubbles expand and then release, creating a beautiful foamy top.

Um, but why Diet Coke? The unscientific reason is that diet soda works better than regular soda due to the artificial sweetener. And, honestly, Diet Pepsi works just as well as Diet Coke as our willing young interns discovered.

"The Diet Pepsi worked even better than the Diet Coke," explains Sarah, soaked and sticky after the experiment.

"I thought it would take more time for the Mentos and the soda to interact," Don says in amazement. "But the two instaneously combusted."

While our blasts didn't match the 18-20 foot gusher we saw on the Internet, our Mentos-soaked soda fountains surprised all of us by leaping at least 10-12 feet off the ground. Which may have explained the odd looks we received from on-lookers to our offices after our experiment.

With Independence Day just around the corner, why not try to celebrate the Fourth with a spectacle of a different sort. Mentos and Diet Coke may not take place of fireworks but it'll give ya one heckuva show.



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