Clean or Green Penny Activity | U.S. Mint for Kids (2024)

FAQs

Clean or Green Penny Activity | U.S. Mint for Kids? ›

In Bowl 2, pour in some vinegar and salt. Swirl or stir to dissolve the salt. Within about 30 seconds, the pennies in this bowl will start to shine. The vinegar and salt mixture dissolves the outer layer of dirt.

Conclusion: We found that the vinegar did the best job of cleaning the coins. No-one predicted this. This is because the vinegar contains an acid which helps to dissolve the dirt. Cola also contains this acid, but not as much.

If you are genuinely wanting to know how to clean pennies, I have learned that a mixture of vinegar and table salt will get them really clean and shiny. Soak them in the solution for a couple of minutes.

To clean about two dozen, stir ¼ cup of white vinegar and 1 teaspoon of salt until the salt dissolves in a non-metallic bowl. Soak the pennies in the mixture for five minutes. Rise really well under running water and place on a paper towel to dry. Another method requires a pencil with a fairly pliable eraser.

The copper mixes with oxygen, the same gas that we breathe. This cause something called oxidation and makes the penny look dirty. Lemon juice has acid in it that removes the dirty color or oxidation and makes the penny nice and shiny again!

Experiment with other products

Ketchup contains vinegar and tomato acid, which can dissolve copper oxide. Simply apply a small amount of ketchup to the penny and rub it with a cloth or toothbrush for a few minutes. Rinse the penny with water and dry it off with a towel.

When copper oxidizes, it turns a blue-green color, forming a compound called malachite. In Bowl 2, the vinegar and salt create a chemical reaction. This reaction dissolves the copper oxide (the dirty looking spots) and some of the copper on the outside of the penny. The result is a shiny looking penny!

How to turn pennies green? ›

How it Works: The vinegar, which is an acid, will dissolve the copper oxide layer of the pennies. This will allow the copper to easily mix with oxygen in the air. The copper and oxygen, along with chlorine from the salt, will combine to create the blueish-green compound malachite.

Those tart little lemons work to remove copper oxide because they contain citric acid. Since lemon juice has the highest concentration of citric acid of any fruit, it works the best. Other juices that rank highly include lime, grapefruit, and orange juice.

Pouring vinegar over the pennies helps break up this copper oxide and expose the pure copper on the penny. As the penny dries and is exposed to the air, a chemical reaction occurs and the penny turns green! The green compound is called malachite. You may notice that not all of your pennies turn green.

After a few minutes, the same reaction that dissolves stuck-on grime can begin to eat away at the copper. This may cause the pennies to give off an odd metallic residue, staining your hands or the container they're in.

Copper oxide dissolves in water, but it usually takes a long time. The combination of vinegar (a weak solution of acetic acid), and table salt (sodium chloride) helps to dissolve the copper oxide, and also forms the blue copper(II) ion, which is soluble in water. The penny becomes shiny again!

Pickle or lemon juice works best. Let the pennies sit.

The copper mixes with oxygen, the same gas that we breathe. This cause something called oxidation and makes the penny look dirty. Lemon juice has acid in it that removes the dirty color or oxidation and makes the penny nice and shiny again!