Popcorn 
Popcorn pops because of a combination of temperature, pressure, and phase change.  When the temperature increases, the liquid water inside the kernal changes to a gas.   Since water in it's gaseous state expands, the pressure inside the kernel increases.  This makes the pressure inside the kernel greater then the pressure outside, and voila - you have popcorn!
Posted by pwilson On 24 October, 2012 at 9:23 AM  

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