Diet Coke explodes when you drop mentos in it, most people have seen it, if not done it themselves, but why? Well, there are a lot of parts to answering this question. First of all, why Diet Coke? Well, Diet Coke generally has slightly more carbonation than regular Coke, which plays into the next part. The bubbles are drawn to the small indentations in the metros, as they search for a way to escape the liquid, which causes a foam, which will create pressure within the bottle eventually causing the explosion. Because mentors are made of many layers, each layer has lots of microscopic bumps that provide a lot of surface area for the carbon dioxide bubbles to grab on to. Because of the increased carbonation in Diet Coke, and the effect of the mentors on that carbonatin the build up in pressure as a result causes the explosion that we all know.