Polishing Pennies


  1. ¼ c Lemon Juice or vinegar
  2. 1 tsp salt
  3. Dirty Pennies
  4. Cup
  5. Paper towels
  6. Several Nuts and bolts

Students will discover that the acid in the pennies removes the copper oxide on the pennies, making them shiny again after being rinsed off. If you remove the pennies from the acid but don’t rinse them off, you can see that they turn greenish-blue as the chemical malachite forms. After many pennies have been cleaned, students can see that if they drop some nuts or bolts into the vinegar, they may attract the copper that has been removed from the pennies and gain  a coppery color. 

Article: https://sciencebob.com/clean-pennies-with-vinegar/