Cleaning Copper Pennies

Do you ever look at the change in your pocket, particularly pennies? Sometimes you get lucky enough to get a newly minted coin that's nice and shiny. Did you ever wonder why those other pennies looked darker? The copper atoms in the penny are attracted to the oxygen atoms in the air to form copper oxide. The pennies look dull and dirty because they are covered with copper oxide. We are going to try an experiment to see if we can clean the copper oxide.

What You Need:

•   20 dull and dirty pennies
•   1/4 cup white vinegar
•   1 teaspoon salt
•   A clear shallow bowl (not metal)
•   Paper towels
•   Spoon

What You Do:

1. Put the salt and vinegar into the bowl and stir until it dissolves.

2. Put the pennies into the bowl for about 5 minutes. Watch them when the