Popcorn has a higher moisture content than other varieties of corn.
Each kernel of corn consists of a soft starch inside and a hard shell outside.
As the kernel is heated, the moisture inside the kernel expands, the soft starch is cooked, and it bursts the outer shell with a pop.
The kernels must contain at least 13.5% water in order to explode.
For more popcorn facts from the Encyclopedia Popcornica, check out The Popcorn Board’s website http://www.popcorn.org