Have you ever wondered why some pennies are shiny and some are dull? It’s not just dependent on how old the pennies are. Chemical reactions are responsible for the change in a penny’s appearance over time.
Kids will love trying their hand at the classic cleaning pennies science experiment to see if they can use a chemical reaction to make pennies shine brightly once again.
Cleaning Pennies Science Experiment
If you have dirty, dull, or green pennies lying around, try the cleaning pennies science experiment to turn them bright again! You need just a few things for this experiment:
- Dull pennies
- Small container (we used a beaker)
- Paper towels
Create a solution of vinegar and salt using one teaspoon of salt and 1/4 of a cup of vinegar. Mix until the salt is dissolved (it helps if the vinegar is a little warm). Add the pennies.
Wait about 5 minutes, then remove the pennies from the solution. Dry the pennies with a paper towel.
The pennies will be cleaner and brighter than before.
Repeat the experiment with the same pennies in a new solution of vinegar and salt and see if you can make them even brighter!
Will using lemon juice and salt have better results than vinegar? Try other materials containing small amounts of acid to see which produces the best results. Ketchup and oranges have a high acid content as do vinegar and lemons.
Cleaning Pennies Science Experiment Explained
Pennies turn dull and green due to oxidation. Over time, pennies form a layer of copper oxide on the surface of the penny, which actually protects it from further corruption. After quite some time, or after exposure to an acid, pennies will form copper sulfate, carbonate, and chloride salts, which gives pennies a green color. Washing the pennies in a vinegar and salt solution removes the patina from the pennies, exposing the brighter copper underneath once more.