how does popcorn pop?

The outer shell of the popcorn kernel is watertight. As the popcorn gets hotter in the oil, the water on the inside gets hotter and hotter until it explodes.

Most popcorn increases in volume between 30-50 times when popped, so one cup unpopped will make between 2-3 gallons of popped popcorn.

If you are making it on the stove put 1/4" oil into the bottom of a heavy pot. Put four or five kernels into it as the oil heats. As soon as the kernels have popped, add in the rest of the popcorn(usualy 1/3-1/2 cup). Put on the lit with a small gap for steam to escape. Do not shake or stir but leave on high heat until the popping slows down. Remove from heat for one minute to let popcorn finish popping, then dump into a bowl.

If you want the thermodynamics of it... here's how it works...

As water is heated the enthalpy is increased, at ambient temperature the water is held relativly stagnet untill it reaches the "flash" point, at which it will become steam. Because the steam is enclosed in the kernel, it build pressure to rupture the husk of the kernal. The cellulose structure inside of the kernal will hold together even after the hard and brittle husk is broken apart. Kernals that don't pop are either too low in moisture content, or release steam without actually rupturing the kernal.

There is a tiny bit of mouisture inside the kernel, that, when heated "explodes" and forces the kernel to turn inside out. This creates the pop corn.

The water molecules inside the kernel heat up and release enough energy to turn the kernel inside out.

popcorn pops obviously because the kernels get extremely hot in the microwave. do you have blonde hair?hahahahaha

by the chemical reaction and the heat