That penny's not a lemon. Just shine it up!

There's SO much you can do with lemon juice - including shining up a copper penny. 

This little experiment is a fun way for kids to see what an acid can do. 

What You Need
Dull pennies from before 1982 (they contain 95-percent copper)
cup
lemon
knife (for use by grown-ups only)

What to Do
Rub a lemon under the heal of your hand against a table/counter. This will help release the juices after it's cut. Have an adult cut the lemon in half.

Kids should squeeze the lemon so the juice runs into the cup. Squeeze hard. (Don't worry if a few seeds drop into the cup.)

Drop a penny or two into the glass. Make sure it's completely submerged in the lemon juice and that the pennies aren't overlapping.

Wait 5-10 minutes.

Remove the pennies and wipe with a paper towel. Look how much shinier they are now!

Disappointed in the result? Soak it longer!

We started with four pennies, all of which were equally brown. The two we kept out of the lemon juice were our control, and made it easy to see how much brighter the juiced pennies were.

How it Works
Dull pennies aren't just dirty. Oxygen in the air has reacted with the copper to form a copper oxide coating. The juice from lemons contains citric acid, which effectively releases the coating from the penny, renewing its shiny appearance.