What Is a Tarnished Penny

The negatively charged oxygen atoms in our air are attracted to the positively charged copper atoms in the penny. When oxygen binds with copper, they form a new molecule known as copper oxide. … This is why most pennies you see look dirty or tarnished—it’s not actually dirt but copper oxide that makes them look so dull.

Is a tarnished penny a chemical change?

Tarnishing is properly considered a chemical change.

How do you tarnish a coin?

1. Add 1 part bleach to 1 part water directly into the plastic bowl. Place your coins into the mixture and set aside for one hour. …
2. Remove the coins from the bleach and rinse with water. Pat dry with a towel or air dry the coins.
3. Rub the emery board over the sides, front and back of the coin.