I am fascinated by the chemistry of pennies. Dissolving a penny in nitric acid is one of the most visually stimulating chemistry reactions I have ever seen. The combination of a bubbling green solution and noxious brown gas that changes the color of an acid base indicator enlivens any discussion on redox chemistry. Likewise, the golden penny experiment is pretty cool, too. In this experiment, a penny is plated a penny with a silvery zinc coat that subsequently turns a golden color when heated. There are a large number of other chemistry experiments that use pennies. Erica Posthuma-Adams recently described a boat building experiment in which students design and build boats; pennies are used as weights to test each boat’s seaworthiness. Finding the density of pennies is a classic chemistry experiment.
My favorite penny experiment is melting pennies. It is simple to conduct and it can be used to discuss a variety of chemistry topics. Check out the video below.
I would love to learn more about the chemistry of pennies and other coins. If you have any experiments to share, I would enjoy hearing from you.
You can find out more about the composition of pennies as well as more experiments to do with pennies in the Journal of Chemical Education. A small sample of articles on pennies is listed below.