Abstract
The Diet Coke and Mentos experiment involves dropping Mentos candies into carbonated beverages to produce a fountain. This simple experiment has enjoyed popularity with science teachers and the general public. Studies of the physicochemical processes involved in the generation of the fountain have been largely informed by the physics of bubble nucleation. Herein, we probe the effect of ethanol addition on the Diet Coke and Mentos experiment to explore the impact that beverage surface tension and viscosity have on the heights of fountains achieved. Our results indicate that current descriptions of the effects of surface tension and viscosity are not completely understood. We also extend and apply a previously reported, simplified version of Brunauer–Emmett–Teller theory to investigate kinetic and mechanistic aspects of bubble nucleation on the surface of Mentos candies in carbonated beverages. A combination of this new theory and experiment allows for the estimation that the nucleation sites on the Mentos candy that catalyze degassing are 1–3 μm in size, and that between 50,000 and 300,000 of these sites actively nucleate bubbles on a single Mentos candy. While the methods employed are not highly sophisticated, they have potential to stimulate fresh investigations and insights into bubble nucleation in carbonated beverages.
Highlights
Dropping Mentos candies into a freshly opened bottle of Diet Coke is a popular experiment among science teachers and the general public [1,2,3,4,5,6,7,8,9,10]
Because surface tension decreases and viscosity increases with ethanol addition [28,29], these results demonstrate that neither the surface tension nor viscosity of a beverage can be linked to fountain heights in a straightforward manner
A variety of methods were used to explore the effect of ethanol on the kinetics of degassing and bubble nucleation in the Diet Coke and Mentos experiment
Summary
Dropping Mentos candies into a freshly opened bottle of Diet Coke (or other carbonated beverage) is a popular experiment among science teachers and the general public [1,2,3,4,5,6,7,8,9,10]. Insight into the physical chemistry involved in fountain formation has been uncovered by studies on the kinetics of degassing and bubble growth in this experiment [6,7,8,9,10]. Further understanding of the relevant processes has been guided by studies on nucleation and bubble growth in Champagne and other carbonated beverages [11,12,13,14,15,16,17,18,19,20].
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