Cleaning Pennies

The Action

Dirty pennies will become clean again.

Grade Level

Grade 6 - Chemicals and Reactions

Grade 8 - Solutions

Grade 9 - Chemistry and You

Grade 10 - Chemical Change


Several dirty pennies

Salt (NaCl)

White vinegar (acetic acid)

Small clear glass bowls or dishes (petri dishes work too)

A beaker of water (250 ml is enough)


Fill one of the small bowls half full with vinegar. Stir in approximately 1/2 teaspoon of salt. (Note: The more salt present in the solution, the faster the reaction will be.)

Place the pennies in the vinegar and salt solution. Wait until they are clean and then rinse them in the water.


No safety concerns, except do not drink the vinegar solution, especially after cleaning pennies.


Make sure to rinse the pennies off in the water or a blue residue will be left behind.

Science Principle

This experiment demonstrates a chemical reaction. The vinegar and salt react with the topmost layer of copper on the penny. This removes the dirt and top layer of copper leaving a clean layer of copper exposed.

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