The simplest way to tell if something is copper is by its appearance, which is a unique reddish tone before oxidation. Its color turns green when oxidized. Copper also has several other notable properties, such as a high level of thermal and electrical conductivity, as well as specific strengths against a variety of stresses. Copper is extremely common in human use, both in piping in its pure form and in alloys such as brass and bronze in such forms as doorknobs and sculptures.
If an object's appearance does not show that it is copper, or if someone suspects that it is just a copper plating or paint, there are other ways to check. The least destructive ways are to weigh it, or to check its electrical conductivity. Copper weighs about 0.3 ounces per cubic centimeter, so if one have an easy way to calculate the volume of material, he will be able to predict a copper object's weight. The electrical standard potential of copper is either 0.522 volts or 0.345 volts, depending on the type. This may be misleading, however, because a thick enough coating of copper will conduct electricity by itself. Pure copper is relatively soft and is easily scratched with common steel tools.