Sorry, would-be pranksters: freezing Mentos in ice cubes and then putting them in soda doesn't cause the soda to fizz up. But why doesn't it work?
It's because when you get the Mentos wet, their pitted candy surface starts to dissolve. And without a surface that's covered with thousands of little pits, there's nowhere for the carbon dioxide to go, which is what creates the fizz. Instead, you just have a gross soda. Too bad! Pretty amazing that it took this long for someone to actually try this prank, eh? [Steve Spangler Science]