Yellow pop corn pops up much larger than white--expanding 40-46 times its original size.  White pop corn enlarges about 35-40 times its kernal size.

 
 

	Why pop corn pops?  Every kernal of pop corn contains certain amount of moisture inside.  A thin hard covering called the "enamel" holds the moisture within the kernal.  When heat is applied, the moisture inside the kernal turns into steam.  As the steam pressure builds up and has no place to go, an explosion occurs.