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Polishing Pennies Experiment

Polish dirty and old pennies to a shiny finish with this cool experiment!

Topics: Oxidation, Acids, Reactions

Difficulty: Easy to do and see results


  • Dirty pennies (15)

  • Lemons (or Limes)

  • ¼ cup white vinegar

  • 1 teaspoon salt

  • 2 Plastic bowls

  • 2 nuts and 2 bolts

  • Paper towels

Note: Parental Supervision is recommended for all experiments. You may also want to wear gloves for this experiment.


1. Pour vinegar into the bowl #1, mix salt and stir it (dissolve the salt)

2 . Put 5 dirty pennies into the bowl and wait for 10 seconds

3. Take out the pennies, rinse them out in some water

4. The pennies will be clean and shining now

5. Put 5 more pennies to the bowl and after 10 seconds put them in the paper towel for drying. The pennies will show a greenish-blue tinge.

6.Now put the 2 nuts and bolts in the water, you will see them taking the color of Copper

How it works

Pennies are made of 88% Copper and 12% Nickel. The Copper in pennies react with Oxygen forming Copper Oxide, causing the pennies to appear dull and dirty. Vinegar is an acid and the acid reacts with the salt to remove the Copper Oxide and make the pennies shine

The greenish-blue tinge we see is caused by the formation of malachite, a copper compound.

Due to the acidic nature of vinegar, it removes some of the copper from the pennies, leaving this dissolved copper in the vinegar mixture. This copper then gets attracted to the metal in the nuts and bolts, so they take the copper color.

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