Coke and Mentos

Quicktime Video, about three minutes. Long load time. Sorry, but it's worth it.

Via various ScienceBlogs posts comes this wonderful, gorgeous and geeky video of blowing stuff up. Here, specifically Diet Coke and Mentos, producing a fireworks-like ballet of streaming soda foam.

Now this isn't a chemical reaction, like when as kids we mixed baking soda and vinegar to produce delightful eruptions. Soda is supersaturated with carbon dioxide. I remember as a kid seeing the back room of a soda fountain. A tank of gas, a water hookup, and a pump that forced them together. The interesting chemistry might be why CO2 dissolves so easily. Do other gases do this?

Anyway, the Mentos/soda eruption results from the candy having numerous nucleation sites where bubbles can form. I suspect that bubbles can be nucleation sites leading to a chain reaction.

The childhood experience is not soda and vinegar but root beer and ice cream - making a Black Cow had to be done somewhat carefully to avoid a mess.

And read this post about a bunch of kids designing experiments and testing theories about kinds of candies, sodas, and a penny as a control.

Link