Awesomest Cola & Mentos yet

Yeah, yeah, Cola & Mentos videos are getting somewhat tired. Still, this one really goes overboard:

Ha! Now how does the Cola & Mentos reaction work?

Well, first, the Cola & Mentos thing is a physical reaction, more than  a chemical one: it happens mainly due to nucleation sites provided by the pitted surface of the Mentos candy.This allows for bubbles to form quickly. The candy sink to the bottom, so the pressure form the gas forming at teh bottom of the bottle pushes the water up, rather violently. Gum Arabic (in the Mentos candy) and aspartame (in the Diet Cola) also help the reaction: Diet Cola works better than regular. Gelatin and gum arabic from the dissolving candy break the surface tension, letting bubbles form faster. This paper in the American Journal of Physics actually has surface pictures of Fruit Mentos and Mint Mentos taken with a scanning electron microscope. They checked the nucleation capabilities of both candies, under different conditions in Diet Coke, Caffeine Free Diet Coke, Coca-Cola Classic, Caffeine Free Coca-Cola Classic, seltzer water, seltzer water with potassium benzoate added, seltzer water with aspartame added, tonic water, and diet tonic water. The also used different nucleation surfaces including Mint Mentos, Fruit Mentos, a mixture of Dawn Dishwashing detergent and water, playground sand, table salt, rock salt, Wint-o-Green Lifesavers, a mixture of baking soda and water, liquid gum arabic, and molecular sieve beads They found that the least amount of work needed to create the bubbles was in diet, caffeinated cola. The best nucleation sites were formed on Mentos (no difference found between the Mint and Fruit Mentos).

SEM images of Mint Mentos [(a) and (c)] and Fruit Mentos with a candy coating [(b) and (d)]. The scale bars in each image represent the lengths (a) 200  µm, (b) 100  µm, (c) 20  µm, and (d) 20  µm. The images were acquired with a beam energy of 12.5  kV and a spot size of 5.0  nm. The lower magnification image of the Fruit Mentos has smooth patches in contrast to the lower magnification image of the Mint Mentos, but the candy coating is not uniform. The higher magnification image of the Fruit Mentos is zoomed in on one of the rougher patches

Coffey, T. (2008). Diet Coke and Mentos: What is really behind this physical reaction? American Journal of Physics, 76 (6) DOI: 10.1119/1.2888546

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