Life's Little Mysteries

Why Does Popcorn Pop?

(Image credit: Dreamstime)

Within minutes, a teardrop-shaped kernel no larger than a pea can magically mushroom into a fluffy treat that's at least 35 times its original volume.

The tasty secret: water.

Each popcorn kernel contains a hard outer shell and a starchy inside surrounding a dab of water. When the kernels are heated to about 450 degrees Fahrenheit, the pocket of water turns into steam and expands within the tough casing. Like blowing up a balloon, as more and more steam forms, the pressure against the outer shell increases. When shell can no longer contain the building pressure and finally gives way with the classic pop. The kernel turns inside-out, revealing the softened starch that makes up the white spongy part of your favorite movie snack.

Live Science Staff
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