Thermal conduction in metals

Learning objectives

Students should know that:

• all metals conduct heat well but that some metals are better than others;
• metals that are good electrical conductors are also generally good conductors of heat;
• conduction even in good conductors is a relatively slow process, while in poor conductors it is very slow;
• poor conductors can be used to insulate warm or cold objects.

The thermal conduction experiment

Materials

• Conduction bars (brass, steel, aluminium and copper)
• Heat-sensitivity strips
• Stop clock
• Beaker of hot water

It is advisable to use the 'Nicholl' conduction bars equipment. They are quite expensive but good, and are much better than the individual metal rods or the Ingnhaus.

Groups can use a couple of stop clocks for repeated readings, or for splitting up the group so that one looks at two metals (e.g. copper and brass) while the other looks at the other two (e.g. aluminium and steel). This latter system works well because aluminium and copper conduct heat rather too quickly for the students to read and record at the same time.

Using the worksheet

The Excel worksheet, Thermal conduction in metals, gives the general practical outline. Students should read it on screen, or you can provide a printout. There are real data already shown on the sheet, together with the corresponding line graph. As explained in the Methods, when students replace this data with their own and press 'Return', the new data will automatically be graphed.

Points for further investigation

A number of things can be looked into, depending on time, ability and available resources, once the students have finished the initial (simple) conclusion. Some ideas are as follows:

1. Steel is still a good conductor of heat compared to other materials known as insulators. Find some examples of thermal insulating materials and explain what insulators do.

2. Brass is an alloy of copper and zinc. Looking at the results you have gained for copper and brass, how good a conductor of heat will zinc be?

3. Silver is an exceptionally good conductor of heat. Using the results you have obtained and any information resources you have, explain whether silver is also a good conductor of electricity.

4. Some metals are good conductors of electricity and some are not. Use your results and any information sources to find a link between heat and electrical conductors. Using this, try and explain how metals conduct heat.