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STEM Lab: Dancing Popcorn Kernels!

Demonstrate buoyancy and chemical reactions

By Kim McNeill, Publisher of Southbury-Waterbury CT Macaroni Kid January 25, 2012

Show your kids some science with items you probably have right now. 

What You Need:

  • A clear, tall container
  • 3(ish) cups of water
  • ¼ to ⅓ cup of baking soda
  • ⅛ cup of popcorn kernels
  • ¼ to ½ cup of white vinegar

What You Do:

  1. Mix baking soda and water in the clear container
  2. Add corn kernels
  3. Pour in vinegar.

PRO TIP: Do this part in or near the sink. I'm surprised mine didn't overflow with foam!

Adjust the amounts for whatever size jar/cup/vase you are using.  

Do this for all ages from preschoolers up through tweens. The youngest kids will notice the motion. Make sure they look at the kernels and see that they have bubbles on them. 

For the next age of kids, you can explain how the bubbles are being pushed up by the water (floating), and the corn kernels are being pulled down by gravity. Then explain that when the "buoyant" force of the bubbles is stronger than gravity, the kernel rises. The kernel falls when the bubbles break after they rise to the surface.

The oldest kids can do all of that and perhaps try to figure out how there is gas to make the bubbles. To figure it out, they could even do a science experiment by following the steps below.

  • Try popcorn kernels in plain water.
  • Try kernels in a mixture of water and baking soda.
  • Now put some kernels in water with vinegar.

None of those will show a lot of bubbles on the kernels.

  • Now put the kernels in seltzer water.

Seltzer water has bubbles because it is carbonated. A chemical reaction occurs when baking soda and vinegar are put together; they create carbon dioxide, the same gas dissolved in seltzer water.

See the experiment in action here: