Why Is Your Penny Green?
Create a green patina on a penny (pennies are a copper alloy).
The Statue of Liberty consists of approximately 179,000 pounds of copper. Copper is a reddish-brown metal, but the Statue of Liberty is green. How is this possible?
A chemical change through the process of oxidation the answer. Oxidation is a form of corrosion that occurs when oxygen and moisture in the air attach to certain metals. There's plenty of both oxygen and moisture near the Statue of Liberty, which is made out of copper. Oxidation causes copper and copper alloys to develop a green covering called patina. The patina on copper can help slow down further oxidation or corrosion. The Statue of Liberty's rich green coloring is a trademark for the statue.
Activity:
Create a green patina on a penny (pennies are a copper alloy).
Materials:
Vinegar
Pennies (as many as you would like to use)
Plate (with raised edges)
Paper Towel
Procedure:
Fold the paper towel into a square that can easily be placed in the center of the plate.
Procedure:
Pour the vinegar on the plate so it just barely covers the paper towel.
Now place the pennies on the paper towel. Check the pennies every 12 hours or so. You will start to notice a green patina. This is because the combination of vinegar (aka acetic acid) and pennies makes acetic acid. What side(s) did the patina develop on your pennies, and what does this tell you about corrosion? (HINT: think about oxygen!)
