Copper

Second only to silver in electrical and thermal conductivity, and silver costs roughly a hundred times more per kilogram, which settles the argument for almost every application. Slightly denser than steel, so a copper pipe feels surprisingly heavy for its size. The 210-360 MPa span is annealed to hard-drawn: the same wire doubles in strength purely from being pulled through a die, and softens again if you anneal it.

Properties

Density

8,960 kg/m³ — 8.96 g/cm³

Melting point

1,084.6 °C

Tensile strength

210–360 MPa

Young's modulus

117 GPa

Thermal conductivity

401 W/(m·K)

Thermal expansion

16.5 µm/(m·K)

Floats in water

No

Magnetic

No

What it is used for

• Electrical wiring and busbars
• Domestic water and heating pipe
• Motor and transformer windings
• Roofing and rainwater goods

How it compares

Does it rust?

No. Copper and its alloys cannot rust, since rust is iron oxide. They form a patina instead — copper oxide first, turning to the familiar green carbonate over decades — and that layer is adherent and protective, which is why copper roofs last centuries.

Is it magnetic?

Copper is not ferromagnetic. It is often assumed to be because it is a metal, but most metals are not — only iron, nickel, cobalt and a few alloys are attracted to an ordinary magnet.