Describing Cause and Effect in Popcorn

Popcorn

Everybody loves a big bowl of popcorn to munch on. But do you know how popcorn pops?

Each piece of light crunchy popcorn starts out as a small hard kernel of corn. Technically, it is a seed. But don’t try to bite into it. It is so hard it could break your teeth.

If you want to pop popcorn at home, ask an adult to help you. Put a little bit of vegetable oil and some popcorn kernels in a pot on the stove. Use a pot with a glass cover so you can see inside. Turn on the heat. Shake the pot over the heat. When the kernels get hot enough, they will jump up in the pot. They will make a popping noise. One by one, they will turn into a delicious snack. But how does this happen?

To understand popcorn, think about boiling water. When water boils in a pot, you can see steam rising from the pot. That is because heat changes water from a liquid to a gas. A kernel of unpopped popcorn looks completely dry. But hiding inside each kernel is a tiny bit of water. When a popcorn kernel heats up, the water inside turns into steam. The steam has no place to go. So it pushes out on the kernel of popcorn and causes it to pop.