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ABC news explains the Mentos-Diet Coke explosion (Maker Faire photo by Schody) -
"Water molecules like to be next to other water molecules, so basically anything that you drop into the soda that disrupts the network of water molecules can act as a growth site for bubbles," Coffey told New Scientist. "And if you have rough candy with a high ratio of surface area to volume, then there's more places for the bubbles to go."Low surface tension also helps bubbles grow quickly. Measurements showed that the surface tension in water containing the sweetener aspartame is lower than in sugary water, explaining why Diet Coke creates more dramatic fountains than sugary Coke.
Another factor is that the coatings of Mentos contain gum arabic, a surfactant that further reduces surface tension in the liquid. Rough-surfaced mints without the surfactant did not create such large fountains.
Mentos are also fairly dense and sink rapidly, quickly creating bubbles that seed further bubbles as they rise. Crushed Mentos that fell more slowly created puny fountains that only travelled about 30 centimetres.
"Middle-school teachers are getting their students out onto the baseball field next to their school and doing this reaction, and their students love it," says Coffey. "It's a great way to get students excited about science and learn something new."
Related:
Diet Coke & Mentos Kit - Recreate the Internet sensation in your own backyard! Fresh from their performance at the 2008 Bay Area Maker Faire, the guys at EepyBird have hand crafted replica PVC nozzles just like the ones they use themselves. Each kit contains a variety of nozzle cuts to give you the coolest, highest shooting geysers. We'll even throw in a pack of Mentos to get you started (Diet Coke not included). Check out EepyBird videos here. Thanks again for another great show guys!
