A cross section of a Mad-Dawg gumball shows an outer layer of citric acid and malonic acid, beneath that a layer of food coloring, sugar, and flavoring, beneath that a layer of sodium bicarbonate (NaHCO₃), and finally in the middle-gum! A 12-year-old puts one in his mouth and immediately puckers, smiles, and then foams at the mouth before chewing. Where did the foam come from?

Question

Quizplus · Accepted Answer

The foam came from the reaction between the acids (citric acid and malonic acid) in the outer layer of the gumball and the sodium bicarbonate in the middle. When the two react, it forms an unstable carbonic acid, which quickly decomposes into carbon dioxide gas and water. This gas gets trapped in the gum, leading to the foaming effect.

A Cross Section of a Mad-Dawg Gumball Shows an Outer