Copper properties and uses. Introduction.

page 5

Properties

Metal	Thermal conductivity
copper	394
silver	418
aluminium	238
stainless steel	13

Table 2. Thermal conductivity.
When you heat one side of a material, the other side will warm up. The values above are a measure of how quickly the other side gets as hot as the heated side.

	Thermal conductor

		Copper is a good conductor of heat. This means that if you heat one end of a piece of copper, the other end will quickly reach the same temperature. Most metals are pretty good conductors; however, apart from silver, copper is the best. It is used in many heating applications because it doesn't corrode and has a high melting point. The only other material that has similar resistance to corrosion is stainless steel. However, its thermal conductivity is 30 times worse than copper's.

Picture 4. Car radiator and cooling system made of copper and brass.

Applications

Copper allows heat to pass through it quickly. It is therefore used in many applications where quick heat transfer is important. These include

Device	Uses
Copper plate	Saucepan bottoms.
Copper pipes	Heat exchangers in hot water tanks, under floor heating systems, all weather football pitches and car radiators.
Heat sinks	Computers, disk drives, TV sets.

Part of interactive graphic of thermal conduction

Picture 5 How copper conducts.

	Conducting heat

		Copper is made from a lattice of ions with free electron (see page 4). The ions are vibrating and the electrons can move through the copper (rather like a gas). In picture 5, the left hand end of the piece of copper is hotter. The copper ions at the hot end vibrate more. [Note the electrons have been left out of the picture to keep it clear]. Let's look at just a few electrons and see how they conduct heat from the left to the right. A free electron collides with an ion at the hot end, and gains kinetic energy (it speeds up). It moves to the cold end. It collides with a 'cold ion', making the previously cold ion vibrate more. This heats up the cold end. In this way, energy is transferred through copper, from hot to cold.

Picture 6. A cool lattice. If we heat the left hand end, then the energy will be carried along by conduction.

	Non-metals conducting heat

		Compare this with how heat is conducted in a non metal. The vibrating particles pass on the vibrations to their nearest neighbours. This is much slower. That's why metals are the best conductors - their free electrons can carry the energy along their length.