Kids, have you ever wondered exactly what's behind the popping of popcorn? Here we will demonstrate that both heat and the moisture inside popcorn kernels are necessary for making a perfect bowl of popcorn. You will first need to have an adult partner dry out 1/4 cup of popcorn kernels by placing a single layer on a tray in an oven at 190 degrees overnight.

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

Pop exactly 1/4 cup of fresh popcorn in a hot air popcorn popper, and then do the same with the dried kernels. Measure the volume of each of your results. Some kitchens have large glass measuring cups than can be used for this, or else just use similar sized bowls or drinking cups and "eyeball it".

The fresh popcorn should produce a larger volume of popped corn. Popcorn is mostly starch and water. As the kernel is heated, the water inside turns to steam. So much steam pressure can build up inside the kernel that the outer layer finally cannot hold it back and the kernel explodes. The starch expands into the familiar white substance that we have all come to know as popcorn. So now can you guess why the dried kernels resulted in a lower volume? Most of their moisture was evaporated beforehand, slowly and intentionally, so that there was not enough left to explode the kernel as much.

If you like, you can try different brands of popcorn to see which one gives the highest volume of product. Also try popping old and fresh popcorn of the same brand. Cleaning up from this experiment can be summed up in one word: Enjoy!

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
April 1995

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Reference: Phil Parratore inWacky Science: A Cookbook for Elementary Teachers, Kendall/Hunt Publishing Co. (Dubuque, Iowa), 1994, page 104.