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The Penny Experiment

The Penny Experiment

  Secondary | Materials | Views: 10495

You will need:

  • 20-30 dull pennies
  • 1/4 cup white vinegar
  • 1 teaspoon salt
  • 1 shallow, clear glass or plastic bowl (not metal)
  • water
  • measuring spoons
  • paper towels

What to do:

  1. Pour the salt and vinegar into the bowl.
  2. Stir until the salt dissolves.
  3. Dip a penny halfway into the liquid and hold it there for 10-20 seconds. Remove the penny from the liquid. What do you see?
  4. Dump the rest of the pennies into the liquid. The cleaning action will be visible for several seconds. Leave the pennies in the liquid for 5 minutes.

Note: You want to keep the liquid you used to clean the pennies, so don’t dump it down the drain!

How does it work? Pennies get dull over time because the copper in the pennies slowly reacts with air to form copper oxide. Pure copper metal is bright and shiny, but the oxide is dull and greenish. When you place the pennies in the salt and vinegar solution, the acetic acid from the vinegar dissolves the copper oxide, leaving behind shiny clean pennies.

  • After the 5 minutes required for ‘Shiny Clean Pennies’, take half of the pennies out of the liquid and place them on a paper towel to dry.
  • Remove the rest of the pennies and rinse them well under running water. Place these pennies on a second paper towel to dry.
  • Allow about an hour to pass and take a look at the pennies you have placed on the paper towels. Write labels on your paper towels so you will know which towel has the rinsed pennies.

Design your own experiments with pennies!

Explore chemistry using pennies and ingredients from your kitchen. Household chemicals that can clean or discolour your pennies include baking soda, vinegar, ketchup, salsa, pickle juice, detergent, soap, fruit juice… the possibilities are limited only by your imagination. Make a prediction about what you think will happen and then see if your hypothesis is supported.

We would love to see your own experiments! Send them to us at askanambassador@canterbury.ac.uk or tag us on Twitter @STEMHUB_SE

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