Exploding Kernels

Objectives

• Observe the shape, structure, and texture of corn kernels before and after popping.

• Predict the outcome of an experiment.

• Discuss possible changes to, and different outcomes of an experiment.

Materials

• Per Class:
  raw popcorn kernels (one or more brands/varieties)
  hot-air popcorn popper
  paper
  glue
  pencil or crayons

Key Questions

• Are all the un-popped corn kernels identical? How are they alike?
• How have the kernels changed after being put in the popcorn popper?
• Do you have mushroom of butterfly type popped corn kernels? (See photo in Resource)
• What is happening inside the machine?
• Can you find the kernel hull on the popped pieces of popcorn?
• Where did all the white stuff come from?
• Why might some of the kernels not pop? How might you change these numbers in a second experiment?
• Was your prediction correct?

What To Do

1. Examine the kernels. Observe their size, shape, texture and colour.
2. Choose a number of kernels to experiment with (e.g. 10, 25). Count out that number of kernels from one type of popcorn.
3. Predict (guess) how many of the kernels heated will pop (e.g. 8 out of 10, or more simply: all, some, none).
4. Pop your corn: put your kernels inside the popcorn popper and plug it in. Make sure there is a bowl under the spout of the popper to catch the kernels. Wait until the kernels are popping less than once every 5-10 seconds, then unplug the machine. CAUTION! HOT!
5. Remove any remaining kernels from the machine. Observe your popped and unpopped corn. Count the number of popped and unpopped kernels.
6. Glue 10 unpopped and 10 popped kernels to a piece of paper to see how much space they each take up.

Extensions

• Draw what you think the sequence of popcorn popping looks like. Watcha slow motion video of popcorn popping.
• Try again with a different brand/variety of popcorn, but with the same number of kernels.
• Try the same brand/variety of popcorn but with a different number of kernels. Is the popped vs un-popped proportion the same this time?

Other Resources

Science World | What makes popcorn pop?

National Geographic Kids | How Popcorn Works

Discover Magazine | The Physics of Popcorn