How to Clean Pennies with Vinegar [and Turn Them Green!]

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Penny-Vinegar-Salt-Experiment

Did you now that money is one of the dirtiest things in the world? After all, think about how many people grab money with their hands full of germs and then pass it on. Yuck!

Even though pennies are no longer used often, they do look the dirtiest. Why? Because they are covered in copper oxide, which is formed when copper atoms combine with oxygen atoms. The copper oxide makes the pennies look dull and dirty.

But no fear! We are here today to clean pennies with a simple salt and vinegar solution to make them nice and bright and shiny again!

How to Clean Pennies with Vinegar and Salt

Materials: 

  • Pennies
  • Vinegar
  • Table salt
  • Cup
  • Paper towel or napkin
  • Dish 

Instructions:

  1. Mix about 1/4 cup of vinegar with 1 teaspoon of salt. The exact measurement is not important.
  2. Place a folded piece of paper towel or napkin in the dish.
  3. Carefully dip the bottom half of a penny into the salt and vinegar solution and count to 10.
  4. Take out the penny and observe how shiny the bottom half of the penny is.
    Penny-Vinegar-Salt-Experiment-1
  5. Put all the pennies in the salt and vinegar solution and wait about 5 minutes.
  6. Take half of the pennies out and put them on the paper towel in the dish. 
    Penny-Vinegar-Salt-Experiment-4
  7. Take half of the pennies out and rinse them with water. Put them on a separate piece of paper towel to dry.
  8. After about an hour, look at the pennies in the dish and the pennies that were rinsed with water. Do you see a difference?
    Penny-Vinegar-Salt-Experiment-1-Hour
  9. Leave the pennies in the dish and wait a few more hours. Do you see the pennies turning green?
    Penny-Vinegar-Salt-Experiment-2

Prepare for a lot of “oOOo” and “Ahhhh” from your kids! It’s like magic how the pennies become so shiny and the kids really are amazed that they can do it themselves. 

For more fun with this experiment, you can:

  • Have your child try and wash the pennies with dish soap. Does the dish soap wash off the copper oxide?
  • Try sprinkling salt on pennies and using a dropper, drip vinegar on the pennies. Did the same reaction occur?
  • Lemon juice is also an acid. Try using lemon juice instead of vinegar and see which one makes the pennies shinier?
  • After the pennies dry out, add more vinegar and salt solution and leave them out again to dry. Do more green “stuff” form on top of the pennies?

The Science Behind Cleaning Pennies with Vinegar

Vinegar is an acid, and when mixed with table salt, it forms a solution that dissolves copper oxide. Therefore, when you dip a penny in the solution, it comes out all nice and shiny.

However, as you leave the pennies covered in the salt and vinegar solution on the paper towel, the copper in the penny reacts with the oxygen in the air and form a blue-green colored compound called malachite.

Fun Fact: Why is the Statue of Liberty Green?

Did you know Lady Liberty was once a copper color? When the Statute of Liberty was first unveiled in 1886, it was a shiny bronze color just like a penny. However, as time passed, the copper reacted with oxygen in the air and the statue slowly turned to a dull brown. Then, as the copper continues to react with the water and chemicals in the air, the statute finally turned to the blue-green color it is today.

The statue has remained this color because the exposed copper is now chemically stable and fully oxidized. However, underneath the blue-green layer, the statue is still the original bronze. 

There you go! Next time you see the Statue of Liberty, you can remind your kid of the penny vinegar experiment and how he/she turned pennies blue-green the same way the statue turned colors!

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