Here in this experiment, you can easily turn dull copper into bright, shiny coins.
Things Required:
Dark, dull copper coins
A small, flat container
2 disposable cups
1 teaspoonful of salt
1 tablespoonful of water
2 tablespoonfuls of vinegar
Medicine dropper
Paper towel
Directions:
Place the coins in the container. In one cup, make a solution with the salt and water. Pour the vinegar into the other cup. With the medicine dropper, drop the salt solution on the coins, followed by the vinegar. Repeat these steps and keep the coins in the solution for five minutes. Clean the coins by wiping them off with a damp paper towel.
This Is What Happens:
The coins turn shiny-bright and the dark and dull film is removed.
Science Behind It:
The vinegar (acetic acid), when combined with the salt (sodium chloride) chemically, changes into a weak solution of hydrochloric acid. Hydrochloric acid cleans metals like copper. After a while, the coins will oxidize or become dull and dark again because of the water and oxygen molecules that they come in contact with in the air.
