About this Daily Classroom Special
Why Does Popcorn Pop? was written by Marilyn Chadwick. Marilyn is involved in a collaboration between the New York City Board of Education and the United Federation of Teachers.

History

A Thematic Unit for K-3

Corn is a plant that symbolizes America. When the first colonists arrived, the Native Americans taught them to plant corn. Corn is a truly ancient plant. There are fossils which date it to 2000 B.C. The Inca palace gardens were decorated with gold and silver carvings of maize. Corn was carried to Central America by early South Americans. From there, it made its way north where the Native Americans began to cultivate it and make it a main food crop. The early Americans had many uses for corn including eating it as popcorn. Did you ever wonder why the popcorn pops?

Science Concepts

Corn seeds contain moisture. Heat causes the seeds to pop when the moisture contained in the kernel changes to steam and the kernel explodes.

The Materials

• a few kernels of fresh corn
• one half cup of popcorn
• an electric frying pan
• a few tablespoons of vegetable oil

The Activity

1. Allow the students to handle the fresh corn. Ask: Does the corn appear moist or dry? The fresh corn is moist.
2. Allow the students to handle the dry corn kernels. Ask the same question. The seeds appear dry.
3. Tell the students that a drop of moisture remains inside the dry seed. If you pop the corn in an electric frying pan, you will see condensation on the inside of the cover after the corn pops.
4. Predict: What makes the corn kernels explode?
5. Moisture turns to steam when heated. Steam expands the kernel until it explodes.
6. Make popcorn.
7. Questions:
   • What changes occurred in the appearance of the seed?
   • Were the changes gradual or rapid?
   • Why don't some seeds pop? (outer cover has cracks and the steam escapes without building pressure to pop the seed.)
8. Eat the popcorn.

Note: Use your common sense when popping the kernels. Keep students a safe distance from the frying pan.