I’m not sure if it was my first exposure to the Diet Coke and Mentos geyser phenomenon, but it was the one with the biggest impact—EepyBird’s Extreme Mentos & Diet Coke video, first released in 2006. I loved it. The jump from a single geyser to a choreographed Bellagio-style array of fountains of soda. The likable lab-coated pair releasing the Mentos. The music.
This demonstration has continued appeal. Even more than that, it offers a high-interest opportunity for student (and teacher) exploration. Research has uncovered some information about how the geyser works, but we don’t know everything about it. Tom Kuntzleman, a regular poster on this site, has continued to investigate. He and Trevor Sims authored the Journal of Chemical Education article Kinetic Explorations of the Candy–Cola Soda Geyser last year and now in the May 2017 issue of JCE, Kuntlzeman, et al. open the topic up further with New Demonstrations and New Insights on the Mechanism of the Candy–Cola Soda Geyser, referencing other work on the subject such as Mentos and the Scientific Method: A Sweet Combination by Eichler, et al.
At this point, I’ll leave it to Tom to further pique your interest in delving into the experiment on your own. Visit his blog post Exploring the Diet Coke and Mentos Experiment (packed with great videos!), which he wrote to connect with this Especially JCE column.
More Everyday Materials
If you’ve read some of my previous work related to the Journal, you might know that I’m a fan of chemistry activities that students and I can do with materials I can pick up locally, like at grocery, hardware, and craft stores. Because of this, my other instant “read me” item in the table of contents for this issue was Matsuoka’s Using Silica Gel Cat Litter To Readily Demonstrate the Formation of Colorful Chemical Gardens.
In this demonstration, metal salts (iron(III), cobalt(II), manganese(II), copper(II) chlorides) are added to an aqueous solution of sodium silicate. Silica gel cat litter puts a twist on the delivery of the metal salts. Pieces of litter are placed in each metal salt solution to soak. Then a piece from a solution is added to a test tube of sodium silicate. The author points out the benefits of the litter: “In addition to reducing the preparation time for instructors, the use of cat litter in place of metal salt crystals is superior in that it reduces the volume of reagent consumed.”
Student involvement would likely be limited to observations of the delicate tube-like structures that form in the chemical garden. Most needed materials wouldn’t be available locally. What is the draw for use? The author explains: “As the reaction mechanism in the chemical garden experiment is complex, the aim is not for students to understand the mechanism per se but rather to promote curiosity about science in students through visible tube growth using this experiment. … Furthermore, high school students may learn the sort of development content that may lead to the pursuit of scientific principles such as the difference in the solubility of various salts, the meaning of semipermeable membranes, and osmotic pressure.” For a quick look, take six seconds of your day to watch a time-lapse video showing crystal growth in several of the gardens, available in the demo’s online Supporting Information.
More from the May 2017 Issue
Mary Saecker offers her round-up of all the content from this month’s issue of the Journal. Visit JCE 94.05 May 2017 Issue Highlights. She included the two articles mentioned in this Especially JCE under the heading “New Twists on Classic Activities” and shared an additional link to a past JCE Classroom Activity about a crystal garden investigation.
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