Marilyn Hinds, aged 14, of Afton, Okla., for her question:

What makes popcorn pop?

Every bit of popcorn has lived through an explosion: The explosion goes off with a pop. It splits the kernel of corn and turns it inside out. The soft inside of the kernel is then‑outside. The shiny coat is crisped and curled outside and around the edges.

Corn for popping is especially prepared for exploding. A little bomb is placed right in the middle of each kernel. This bomb is no more than a small drop of moisture.

As the popcorn is heated, this moisture seeps through the soft inside of the kernel, puffing it up. This puts a strain on the outside of the kernel. Finally the moisture turns to steam. Suddenly it needs lots more space, It explodes the way a boiler bursts when all of its water is turned to steam.

In its hurry to get more space, the steam bursts open the popcorn in all directions. Good popcorn may puff up twenty times its original size. And the Indians were enjoying this delicious snack before Columbus discovered America.