Homeschool Science: The Penny Experiment

penny experiment

Cleaning pennies might not seem particularly educational, but this simple experiment is a great way to build on ideas like the scientific method and observation. If you compare older pennies to newer ones, the newer ones are generally shiny and have a more obvious copper color. The older pennies will look a lot darker and muted in comparison. So, how do you go about cleaning them? Here’s how it works:

What you need:

  • 30 old pennies
  • 3 clear cups or containers
  • Water
  • Dish soap
  • Salt
  • Vinegar

What to do:

  • In cup #1, add plain water and ten of your pennies
  • In cup #2, add water, dish soap, and ten of your pennies.
  • In cup #3, add ½ cup of vinegar, 2 teaspoons of salt, and the last ten pennies.
  • Ask your kids which solution they think will do the best job of cleaning the pennies. Have them write down their guesses and any other observations or questions they might have.
  • Leave the pennies in the cups for five minutes. Have your kids look at each cup and notice if there are any changes.
  • After five more minutes, remove the pennies from each cup. The pennies from cup #1 shouldn’t look different at all, water isn’t a great cleaning solution on its own. The pennies from cup #2 should look a little cleaner.
  • Leave the pennies from cup #3 out in the open for a few minutes. You’ll notice they turn a bit green. As the copper in the penny reacts with oxygen and salt, the penny turns green. Just like the Statue of Liberty!
  • Rinse the pennies from cup #3 off, and they should be noticeably cleaner than the pennies from the other two cups.

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