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How Popcorn Pops

This Science Minute was researched and written by Ben S. of Spencer, NY.

Have you ever wondered what makes popcorn pop? Why do some kernels pop and not others?

A popcorn kernel is a hard shell filled with starch and a little bit of moisture. When a popcorn kernel is heated, the water inside the kernel turns to steam. The steam creates pressure inside the kernel causing the starches to expand. Eventually, the outer shell explodes with a familiar "POP."

So why do some kernels pop and not others? Some kernels don't pop because they don't have the right amount of moisture. To pop, a kernel needs to have about 14% moisture by weight. If popcorn is too dry, it won't pop. Other kernels do not pop because their outer shell has a small hole, which allows the steam to escape slowly and keeps the pressure from building up enough to pop the kernel.

So now you know: popcorn is all about pressure!