Pop! Corn!

What's your favorite movie snack? Many people like to eat popcorn while watching movies, how about you? Did you ever wonder what makes popcorn pop? And why can't you use any old kind of corn?

It's quite simple, actually. Popcorn corn contains a lot of water, and it has an unusually hard shell. When the popcorn kernels are heated, they turn to steam. The steam can't escape at first because of the hard shell. But at some point, the pressure inside the kernel gets so high that the shell bursts, and you get a nice fluffy bit of popcorn! If you looked at popped popcorn under a microscope, you'd see that it has lots and lots of tiny holes - this is a structure that scientists call a foam. What other kinds of foam can you think of?

Just how much water is in popcorn? You could look it up, but it's a lot more fun to do an experiment to find out!

What you'll need:
Bag of microwave popcorn
Microwave oven
Kitchen scale
Calculator

Weigh the popcorn bag before popping, and write down your measurement. If your kitchen scale has metric markings (grams), use those because that's how scientists make measurements. If your scale only has markings in ounces, they will work, too. Pop the popcorn according to the directions. When it is done, carefully take it out of the microwave and open the top slightly. Do you see the steam escaping? Be careful, it's very hot! Wait about one minute, then weigh the bag again. The weight should have gone down because water has been lost.

You can even calculate the % water in the original popcorn:
% Water = 100 x (Weight before popping - Weight after popping)/Weight before popping
What value do you get? You can also compare different bags of the same brand, or different brands, to see whether the % water is always the same.