Green Pennies

Have you ever seen the Statue of Liberty, the big, green statue in New York? Well, it was once the color of copper pennies! In this experiment, we will turn pennies into the same green color as the Statue of Liberty.

What you will need:

  • Copper pennies
  • White vinegar
  • Bowl
  • Paper towel


  • Fold the paper towel and place it into the bowl
  • Place the pennies on the paper towel
  • Pour the vinegar into the bowl so that the paper towel is completely saturated, but the vinegar is not pooling over the pennies
  • Allow the pennies to sit in the bowl for at least 2 days (the longer you allow them to sit, the more green they will become). Every few hours, turn the pennies to allow both sides to come into contact with the vinegar. Additionally, pour more vinegar into the dish every time the vinegar has evaporated and the paper towel is dry.

What made the pennies turn green?

A chemical reaction, or the combination of two reactants to form something new, has occurred in this experiment. The vinegar on the paper towel and the copper pennies react with oxygen in the air to form a compound called malachite, or the green stuff you see on the pennies. A similar process also contributes to why the Statue of Liberty turned greenish-blue. The statue would turn greenish-blue due to exposure to oxygen in the air regardless of the presence of vinegar. However, because rain has acid from pollution in it, the rain speeds up the reaction, similar to how the acidic vinegar sped up the reaction with the penny.

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