Cleaning Pennies

Does an acid or a base clean pennies better? Students clean pennies with acidic and basic solutions to determine which cleans copper better. This activity should be done after Mysterious Solutions.



1 qt water + baking soda

1 qt water + Lava soap shavings

1/2 qt lemon juice

1 qt vinegar

4 8-oz. cups for each group

100 dirty pennies


What To Do

DIVIDE the class into groups of four students with the following roles:

  • Materials Handler: Distributes materials.
  • Equipment Handler: Manipulates materials.
  • Recorder: Records results.
  • Speaker: Shares results with the class.


Materials Handlers PASS OUT the following to each group: 8 oz. cup of baking soda solution; 8 oz. cup of vinegar solution; 8 oz. cup of lemon juice; 8 oz. cup of Lava soap solution; 4 dirty pennies.



Equipment Handlers CLASSIFY the substances into acids and bases based on findings from the Mysterious Solutions activity. Lemon juice and vinegar are acids; Lava soap and baking soda are bases.



Equipment Handlers PLACE a penny into each solution. Recorders WRITE whether or not each solution cleaned the dirty penny.




Speakers report their findings to the class. Did acids or bases clean the pennies better?



What's Happening? Find out more about uses of acids and bases.

Challenge: Try cleaning other metals in acids and bases. Which metals are the easiest to clean? Which acids or bases make better cleaners? Share your results in our pH Exchange.

Acid Rain: What is the pH of rain in your area?


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