- a non-metal plate
- white vinegar
- some tarnished pennies (other coins will not work)
- a cloth
Ask: What is the difference between the two kinds of pennies? Is it possible to make the tarnished pennies shine like the new pennies?
Pour some vinegar on the plate. Sprinkle in a some salt and allow enough time for it to dissolve.
Then tell the class that just like you, the tarnished pennies can be made clean again. Drop them into the vinegar-salt mixture. They should begin to become clean in about 30 seconds.
Take the pennies & rub with the cloth until they are clean & shiny. (See also How to Clean Pennies with Vinegar)