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posted by Fnord666 on Saturday April 11 2020, @11:47PM   Printer-friendly
from the coke-is-in-the-air dept.

We now know the effect of altitude on classic "Diet Coke and Mentos" fountain:

Back in 2006, Fritz Grobe and Stephen Voltz—the self-described mad scientists behind Eepybird—ignited an Internet sensation with their viral video of an elaborate version of the Diet Coke and Mentos fountain experiment, recreating the choreography of the Bellagio's world-famous fountain display in Las Vegas. The underlying physics and chemistry of the fountain effect is well-known.

But an intrepid pair of scientists at Spring Arbor University in Michigan wondered whether altitude, and associated changes in atmospheric pressure, would have any measurable impact on the intensity of the foaming fountain and performed a series of experiments to find out. They reported their results in a recent paper in the Journal of Chemical Education. The upshot: If you really want to get the most foaming action for your buck, conduct the Diet Coke and Mentos experiment at high altitudes.

[...] Co-author Thomas S. Kuntzleman first encountered the experiment at an elementary school science fair in 2005, and he has been interested in the underlying physics and chemistry ever since. For instance, he has found that various beverage additives such as sugars, citric acid, and natural flavors can enhance fountain heights. Most recently, he decided to test the hypothesis that the intensity of the fountain effect would be greater at higher altitudes, since one would expect atmospheric pressure to play a significant role in bubble nucleation.

Kuntzleman and his co-author, Ryan Johnson, purchased bottles of Diet Coke from the same store and made sure the bottles all had the same expiration date. For each experiment, they dropped a single Mentos candy into a bottle via a one-inch PVC pipe and then watched the reaction work its magic. They used a graduated bottle/tornado tube to measure the mass lost from the liquid over time. The measurements were all taken within one week of each other, and the team made sure to keep all the bottles at roughly the same temperature.

One set of experiments was performed at different altitudes during a climb of Pikes Peak; another set took place during a drive across North Carolina; and a third set of experiments was performed during Kuntzleman's family vacation, driving through multiple national parks in California, Nevada, and Utah. All told, they performed the experiment at altitudes ranging from below sea level (Death Valley, California) to more than 14,000 feet (Pikes Peak). As expected, they found that more foam was produced at higher elevations.

[...] For those chafing at extended sheltering-in-place orders, it also provides a possible fun DIY group experiment. Identify people in your social circles who live at different altitudes. Each person can do the Mentos and Diet Coke demo—outdoors highly recommended—wherever they are, taking note of the relative heights of the foaming effect, so everyone can then compare their respective results. (Scientific American has helpful instructions, as does Eepybird.)

If you're really feeling ambitious, everyone can do the experiment live simultaneously via Zoom or similar conferencing tool. Just protect your electronic equipment. And be sure to use Diet Coke or Coke Zero, not just because they make the biggest reaction—the aspartame lowers the surface tension of the water—but because they are less sugary and sticky. Trust us, you're going to get soaked.

DOI: Journal of Chemical Education, 2020. 10.1021/acs.jchemed.9b01177  (About DOIs).


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  • (Score: 1, Informative) by Anonymous Coward on Sunday April 12 2020, @09:37PM

    by Anonymous Coward on Sunday April 12 2020, @09:37PM (#981705)

    Because it is a science education journal! Geez Louise, why is it whenever some kind of article like this comes out in some place like Physics Teacher [csun.edu], which this is a similar journal, that foces on undergraduate education, we get our handful of comments like "Hur hur, publish or perish . . . waste of tax dollars . . . stupid academics, I know better."

    Let's take an excerpt from the journal description [acs.org]:

    The Journal serves as a means of communication among people across the world who are interested in the teaching and learning of chemistry. This includes instructors of chemistry from middle school through graduate school, professional staff who support these teaching activities, as well as some scientists in commerce, industry, and government.

    As trivial as you find this, it is real research. It isn't pushinging the boundaries of science forward by a whole heck of a lot, but undergraduate students got to address a problem, conduct research, and analyze their results along with performing supporting calculations. From their abstract:

    Upon further application of the aforementioned principles, a relationship between degassing kinetics, beverage CO2 concentration, and the size of pores on the candy surface that serve as nucleation sites can be derived. Using this relationship and experimental measurements of degassing kinetics, students estimated that the nucleation sites on Mentos candies are on the order of 2–7 μm in dimension.

    How awesome is it to get to do a real research project as an undergraduate? They get hands-on experiment and theory and get to go through the process of a research paper. I would have loved an opportunity like this. My science classes, at least for the first several years, were repeating the same (but important and/or landmark) experiments that were carried out in the late 19th and early 20th centuries. I was doing the exact same labs that students were doing in the same building and room almost 100 years before me, and in some cases on the same lab equipment! It wasn't very inspirational work, especially when you really don't get a grasp on the real significance of those experiments until much later when you get a better understanding of your science and its history.

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