When carbonated beverages (which are supersaturated solutions of aqueous carbon dioxide) are confined within a narrow-necked container, events which rapidly release the gas from solution produce a fountain out of the beverage. One well-known variant of this experiment is the addition of Mentos candies to a bottle of Diet Coke. Previous reports have shown that the presence of aspartame and benzoate in carbonated beverages enhance the fountaining effect. These additives are thought to enhance fountaining by lowering the surface tension of the beverage, but the details of this process are not completely understood. This paper explores the relationship between geyser height and the type of carbonated beverage. It is shown herein that several other compounds commonly found in commercial carbonated drinks such as sucrose, glucose, citric acid, and components of natural flavors also enhance geyser heights. By examining how these additives affect bubbling and foaming behavior in seltzer water, it is postulated that solutes which inhibit bubble coalescence contribute to higher fountains.

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 mm 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.

A slightly modified version of Lotka’s mechanism that gives rise to sustained oscillations is shown to mimic observations of electrochemical oscillations reported during the dissolution of iron from iron electrodes in acidic media. The presentation of the modified mechanism includes only familiar chemical species and, in comparison to other mechanisms of chemical oscillators, is analyzed in a simple manner. Therefore, this new mechanism is particularly well-suited to present to students during introductory discussions on the topic of oscillating chemical reactions.