During World War II, the U.S. Mint switched to zinc-coated steel pennies to conserve copper for military use. However, a small number of 1943 pennies were mistakenly struck in copper ...

A copper penny appears to turn to silver after heating in an evaporating dish with a mixture. The penny then appears to turn to gold when heated in a flame. Heat causes a fusion of zinc and copper to ...

A copper penny is heated and suspended above the surface of acetone in a beaker. The copper demonstrates heterogenous catalysis in the combustion of acetone to carbon dioxide and water. This exotherm ...