Copper is chosen because it can be drawn into long thin wires very easily (it is ductile) and because it is a good conductor of electricity. Metals are also good conductors of heat. This is also due to the free moving electrons. Non-metallic solids conduct heat energy by hotter more strongly vibrating atoms, knocking against cooler less strongly vibrating atoms to pass the particle kinetic energy on. In metals, as well as this effect, the 'hot' high kinetic energy electrons move around freely to transfer the particle kinetic energy more efficiently to 'cooler' atoms. Metals have high melting and boiling points. Strong forces of attraction exist between particles. A large amount of thermal energy is required to overcome the strong electrical forces between the positive ions and the delocalised electrons. These forces operate throughout the lattice.
Metals are lustrous or have a silvery surface but this may be easily tarnished by corrosive oxidation in air and water. The presence of free electrons causes most metals to reflect light. Metals are malleable and ductile. The distortion does not disrupt the metallic bonding. Aluminium is very strong and can be beaten into very thin sheets. It is therefore used in aircraft manufacture. .
A metal alloy is a mixture of two or more metals. Adding another element disturbs the pattern in the lattice so that the layers will not slide past each other so easily. Alloys are usually less malleable and ductile than pure metals and they tend to have lower melting points. They do, however, have other properties which make them more useful than pure metals. Some alloys that we use everyday include steel (used for a wide range of things, including knives and forks, building materials and in cars and ships. The coins that we use are all made of copper alloys. .
Heat treatment: By means of heating and cooling process the strength and hardness of the metal can be changed.