Pennies that look dull and are no longer shiny can be cleaned and in the process the copper can be used to provide a shiny copper coating to a nail. Pennies that are dull have experienced oxidation in the form of a copper-oxygen compound which has formed on the surface. A natural acid can be used to remove the dull oxidized surface. The natural acid is then used to transfer the copper to the surface of an iron nail.
Items Needed for Experiment
- 20 dirty pennies
- disposable cup
- steel wool or sandpaper
- 2 iron nails (not galvanized)
- work gloves
Step 1: Pour about two inches of lemon juice in the bottom of a disposable cup.
Step 2: Place the dirty pennies in the bottom of the cup containing the lemon juice. Non-war time pennies that were minted before 1982 have much more copper content than newer pennies. New pennies only have a thin plating of copper. The remaining metal is actually zinc.
Step 3: Add a pinch of salt to the lemon and penny mixture..
Step 4: Take one iron nail and rub it with steel wool or fine sandpaper. If using steel wool, use the work gloves and be careful not to touch the steel wool to avoid getting any of the thin steel wool pieces in your skin. Set the other iron nail aside.
Step 5: Place the iron nail in the lemon/salt/penny mixture and let the pennies sit about an hour.
Step 6: Pour the lemon juice down the drain, leaving the pennies and nail behind. Never drink the lemon juice used in this experiment. The residual liquid left in the juice can make you sick. Throw away the cup after using it for the experiment also.
Step 7: Look at the nail. Compare this nail to the nail that was not placed in the lemon/copper solution. What do you see? Is any copper plating now on the nail?
Lemon juice is a natural acid that attacks the oxidized copper-oxygen bond, releasing it from the surface of the pennies. The oxygen ends up as bubbles that can be seen starting slowly, but almost foamy in appearance by the end of about an hour. The copper ions that are floating around in the lemon juice are attracted to iron. The copper ions build-up around the iron nail to create a thin coating. Ions are atoms that either have extra electrons or are missing electrons. This process is similar to the process used to make metal plating on other metals.
Check out a similar science experiment that uses any dark cola like Coke or Pepsi to actually clean pennies HERE.