Science Behind Coke & Mentos

Science is all around us, even in sodas and candy.

A favorite science experiment among students is taking Mentos candy and dropping it into a Coke or Diet Coke. The reaction is a geyser of Coke spraying a fountain of bubbly brown liquid into the air.

Misconceptions

In 2006, scientists on the Discovery Channel hypothesized that the fountain of Diet Coke was a chemical reaction created from mixing the gum arabic and gelatine of the Mentos and the potassium benzoate, caffeine, and aspartame of the Diet Coke. Recent research shows, however, that the reaction is not a chemical, but a physical reaction.

Expert Insight

After further study, experts have determined that the reaction is caused from a mix of a rough surfaced candy with low surface tension in the liquid. The roughness of the candy disrupts the bonding of the water molecules, creating bubbles.

Considerations

Diet Coke creates a bigger geyser than Coke because aspartame, which is only in Diet Coke, lowers surface tension in water. The gum arabic in the Mentos further lowers the surface tension.

References

• Science Buddies: Coke and Mentos
• New Scientist: Science of Mentos-Diet Coke Explosions Explained
• ABC News: Science of Mentos-Diet Coke Explosions Explained