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What’s in a Penny?

What’s in a Penny?

January 23, 2020

What happens when the metal in a coin is worth more than the face value of a coin? This has happened several times in the history of the United States resulting in the Treasury Department changing the metal composition of coins. These changes to metal composition provide opportunities to explore what’s on the inside of pennies. With only a few common household items, you can explore the differences between pre and post-1982 pennies.

Items Needed:

  • 2 pennies (1 from 1981 or earlier and 1 from after 1982)
  • Lemon cut in half
  • Lemon Juicer
  • 2 jars or glasses
  • Needle-nose pliers
  • Safety glasses


  1. Ask an adult for help with this step. Have an adult take the needle nose pliers and snip a small notch into the edge of each penny.
  2. Put one penny in each glass or jar.
  3. Take one half of the lemon and place it in the lemon juicer. Squeeze the juice into one of the cups. Wearing safety glasses during this step is important to prevent any lemon juice from getting in your eyes.
  4. Repeat this step with the other half of the lemon and other glass.
  5. Now it’s time to wait! You should see bubbles begin to form in the glass with the post-1982 penny, which indicates a chemical reaction is taking place.
  6. Check on the pennies in a few days – Rinse the pennies and carefully examine them. Be careful handling the pennies as they may be sharp
  7. What happened to the post-1982 penny? What do you notice between the two pennies?

Penny for your thoughts?

You should notice that some of the core of the post-1982 is missing. This is the result of the bubbling witnessed while the penny was in the lemon juice. Today’s pennies are 99% zinc core with a thin copper plating. This zinc oxidizes in the citric acid and then dissolves in the solution. Little to nothing will happen to the pre-1981 penny because it’s mostly made of copper.

Pennies produced before 1982 were made of mostly copper. Due to inflation in the 1970s, the value of the metal in the penny was worth more than it’s one-cent face value, resulting in the Treasury Department changing the metal make up of a penny and finalizing that make up in 1982. You can expand on this experiment by testing pennies from 1982 only. Some pennies from this year had copper cores and some had zinc cores. Which ones will you find?