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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.
Materials
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 1 qt water + baking
soda
 1 qt water + Lava soap shavings
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 1/2 qt lemon juice
1 qt vinegar
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 4 8-oz. cups for
each group
 100 dirty pennies
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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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