Page 168 - Science Coursebook

11.4 Conduction of heat

Sarina is stirring a hot drink. She is using a metal spoon.
Soon the handle of the spoon is too hot to hold.

The drink is hot. It is a store of thermal energy. Some of the
energy goes into the spoon and travels up the handle. When
Sarina touches the handle, it feels hot.

Question
1 If Sarina used a plastic spoon, would she notice the Why does the spoon get hot?
same thing?

Conduction
Sarina has observed the process of thermal conduction (or heat conduction).
Energy is travelling from a hot place to a cooler one through the solid metal of
the spoon.

We use the term ‘conduction’ because this is similar to electrical conduction which
you studied in Unit 10. But remember that here we are thinking about energy
travelling through a material from a hot place to a cooler place.
The picture below shows one way to observe thermal conduction in a metal rod.

The rod has several drawing pins (thumb tacks) attached to it using wax. One end of
the rod is heated using a Bunsen burner.

Gradually, energy spreads along the rod. The drawing pins drop off one by one, as the
rod gets hot and the wax melts.

Observing energy conducting along a metal rod.

Activity 11.4A

Comparing metals

Your teacher will show you rods made of several different metals.
Discuss how you could adapt the experiment shown above in order to compare
these metals. How will you decide which metal is the best thermal conductor?

166 11 Energy

A+E SE