At-Home STEM Activities: Chemical Reactions with Pennies

This chemistry experiment uses an acid, vinegar, and, a base, salt, in one bowl to clean copper pennies, and in another bowl, just vinegar to turn a penny green! When dirty pennies are placed in vinegar and salt, the copper oxide on and some of the copper on the penny dissolve in the water and is removed from the pennies surface. When the penny is rinsed off and wiped clean, it looks brand new! When a penny is soaked in just vinegar, it speeds up the process of oxidation and over a few hours the penny will be greener.