Heat Conductors

Heat Conductors

You will need: Wire, glass rod, wooden rod, candle.

We speak of certain materials as being good conductors of heat and others as poor conductors. By this, we mean that whereas one material will readily absorb and pass heat along its length, another will resist it and try to confine the heat to its source.

An ordinary candle flame will permit us to perform a few simple experiments to show the relative heat conductibility of various types of materials.

First, hold a glass rod to a candle flame. No matter how long you keep it there, the end of the rod which you are holding will remain unaffected by the heat at the other end. This is because glass is an extremely poor conductor of heat.

Be careful when you remove the rod from the flame, however. Glass always looks so deceptively cool-and this will not be the case with the end of the rod which has been held to the flame. In fact, it will be uncomfortably hot. So take care.

Now try the same experiment with a wooden rod. The end of this will char and may possibly flame up after it has been held to the candle for a few seconds. The end which you are holding will remain cool because wood is also a poor conductor of heat.

Finally, take a length of wire and hold one end of this in the candle flame. Be prepared to drop the wire suddenly, however, for within a very short time the wire will have conducted heat from the candle flame to your finger tips to an uncomfortable degree.

This will prove that although glass and wood are poor conductors of heat, metal is a good conductor. Perhaps you can answer the following question now: Why do saucepans and kettles have wooden handles?