Polishing Pennies

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In this experiment, learners try different liquids to see which ones clean pennies best. Liquids to try include water, lemon juice, cola, vinegar, and dishwashing detergent. Suggested extensions include trying vinegar with table salt, vinegar with cream of tartar, salt, and dishwashing detergent, tomato ketchup, and water and baking soda. Learners should find that acidic liquids are better cleaners, since they react with the copper under the "dirty" outer layers of copper oxide, allowing the "dirty" parts to be rubbed away. This activity could be combined with a lesson about the Statue of Liberty, which is made of copper and shows signs of copper oxide on its surface.

Quick Guide

Preparation Time:
5 to 10 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$1 - $5 per student

Age Range:
Ages 6 - 14

Resource Types:
Activity, Experiment/Lab Activity

English, Spanish

Materials List (per student)

  • Masking tape
  • Pen
  • 6 Small disposable plastic cups (3 oz.)
  • 5 Old, dull pennies
  • Water
  • Dilute liquid dishwashing detergent (1/4 teaspoon detergent in 1 cup of water)
  • Disposable plastic spoon
  • Lemon juice
  • Cola
  • Vinegar
  • Table salt (optional)
  • Cream of tartar (optional)
  • Tomato ketchup (optional)
  • Baking soda (optional)
  • Paper towels
  • Clock or timer


  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
      • Solutions
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations


To use this activity, learners need to:

  • see
  • see color
  • touch

Learning styles supported:

  • Uses STEM to solve real-world problems
  • Involves hands-on or lab activities


Access Rights:

  • Free access