|#5: Mentos in Diet Coke or Diet Pepsi|
I actually could only get 4 Mentos in the Pepsi before it exploded on me.
As you can see, Diet Pepsi won out on our test by a landslide.
Why does this reaction happen with diet soda and Mentos?
It is caused by something called nucleation. Bubbles of carbon dioxide "nucleate" shortly after the pressure is released from a container of carbonated liquid. Nucleation often occurs more easily at a pre-existing "interface", or a surface forming a common boundary among two different phases such as using string to make crystals form rock candy from a sugar-water solution. The surface of the mint Mentos is such an interface, as it is covered with many small holes that increase the surface area available for reaction, thereby allowing CO2 bubbles to form with such a rapidity and in such a quantity that a geyser is formed. A 2006 episode of the television series MythBusters reported that when fruit-flavored Mentos with a smooth waxy coating were tested in carbonated drink there was hardly a reaction, whereas mint-flavored Mentos (with no such coating) added to carbonated drink formed an energetic eruption.