Diet Coke and Mentos: Why the Reaction?

By JJ HERMES

It's been well documented, both by David Letterman and in thousands of YouTube videos, that combining Mentos breath mints with Diet Coke produces a thrilling eruption. But why?

Tonya S. Coffey, an assistant professor of physics and astronomy at Appalachian State University, had her sophomore-level physics students answer that question, and...