The only problem was our pennies, usually dug hastily from the bottom of my purse amid the chorus of pleading children, were quite tarnished. I decided we would have to clean them, before turning them into a bracelet - that's where the science came in.
The grimy tarnish on pennies is actually a layer of copper oxide. It's what you get when copper, the outer layer of a penny, combines with the oxygen, from the air around it. To remove the copper oxide, we needed to turn it into something water soluble, so we could wash it away, and expose the fresh shiny copper underneath. We used ketchup, which contains vinegar, an acetic acid. Acetic acid combines with the copper oxide, to form copper acetate, which dissolves in water (it helps if you use your very best Ben Stein, science teacher voice, to explain that to your children).
However, our experiment had varying results. Our pennies were cleaner, but only a little shinier. We're currently, trying out a vinegar soak, on some of the other pennies. Maybe, we'll try Coke verses hot sauce next. In the meantime, my oldest daughter, happily accepted the bracelet, tarnish and all, and was last seen carrying it back into the wasteland from which I had rescued the pennies in the first place.
It's great to be a homeschooler.