How does the popcorn "POP" in the microwave?

Question

Where does the white part come from?

Answer 1

The pop is due to the water trapped inside of the corn kernel.
The microwave heats the water untill it turns to steam and explodes the inside of the kernel.

The white part is the inside of the kernel that has been cooked and puffed up from the steam.

Answer 2

Popcorn, like all six types of corn, is a cereal grain and originates from a wild grass. Its scientific name is zea mays everta, and it is the only type of corn to actually pop.
Popcorn is made up of three main components; endosperm, germ and the pericarp. The endosperm is made up of soft and hard starch granules. The endosperm is always white or yellow in color and is a carbohydrate. The function of the starch is to provide energy for the living part of the kernel, more commonly known as the "germ" or "embryo." The outer hull of the kernel is the pericarp, which is made of cellulose. The pericarp or hull is usually white or yellow in color, though the range of colors includes red, black and many colors in between.
Popcorn needs heat to pop. Most popcorn will pop when the kernel's internal temperature reaches 400-460 degrees Fahrenheit. Bound within the endosperm or starch is moisture. When the kernel is heated, the moisture turns to steam. Because the pericarp or hull is hard and flinty, pressure builds up within the kernel. The starch inside the kernel becomes soft like gelatin and the moisture vaporizes until the pressure in the kernel reaches 135 pounds per square inch. The pressure increases until the pericarp or hull ruptures and the gelatinized starch granules puff out. The kernel literally turns inside out. The starch or endosperm is the white part of the popped kernel and the pericarp or hull is the darker, flaky bit at the center of the kernel.

Answer 3

Yep, Dave's got it right. Same goes for popcorn made on the stove or in the movie theatre. Heat makes the water inside the kernel expand causing the POP!

***CLAPS FOR DAVE***

Answer 4

The inside of the kernel heats up and basically explodes. The white stuff is the starch from inside the kernel.

Here are some sites with good info:
http://www.nal.usda.gov/speccoll/images1/popcorn.html
http://www.nasa.gov/audience/forkids/home/popcorn.html
http://recipes.howstuffworks.com/question255.htm

Answer 5

Dave pretty much nailed it....there is water inside the kernal that makes it POP when it gets hot.