Why Does Vinegar Clean Pennies?
Cleaning pennies with vinegar is one chemistry experiment that you can do at home. Your kids will surely be amazed at the cleaning effect of vinegar on pennies. This experiment is easy to do and all the materials that you need can be found at home.
The reason for the success of using vinegar to clean pennies is the chemical reaction that happens when a penny is placed in a bowlful of vinegar. Pennies are made of copper. That is why new pennies are usually shiny because they have not been exposed to the air while old pennies look dull and greenish.
Old pennies can be easily restored to its shiny condition. The crust is not a stain but a crust of copper oxide. When the oxygen in the air reacts with the copper of the penny, it forms a green crust on the surface called a copper oxide. The oxygen and the copper are bonded chemically forming this crust.
Vinegar on the other hand is an acid solution. Vinegar that is used for home use usually has about 5% of acetic acid in it. This diluted form of acetic acid is effective as a safe household cleaner.
This acid is what dissolves the copper oxide that has formed in a penny. When the crust is dissolved, it will expose the shiny surface of the copper penny underneath. The reaction of the acid when it gets into contact with copper oxide is that it breaks the bond formed by the oxide. When the bonds are broken then it dissolves away combining with the acid.
This is what happens when you soak old and dull pennies in a bowlful of vinegar. What comes out after a few minutes is a penny that is restored to its original shine. The copper from the oxide is now mixed with the vinegar that could be used for other purposes.