2.3 Understanding thermal energy

16 October 2010

Order these objects in the lab from coldest to warmest. Go touch them to help you decide.

Wooden deskMetal tapPlastic whiteboardTiled floorConcrete wall

Conduction

• Atoms vibrate, the higher the temperature the greater the temperature.

• Metals are the best conductors as they have lots of free electrons.

Activity A

• Imagine heating up some baked beans in a metal saucepan. You stir the beans with a metal spoon. Using the idea of conduction, explain why the spoon gets hot.

Convection

• The atoms in fluids are free to move. When they do so they transfer heat – this is called convection

Activity B

• Now imagine heating up some soup. Even if you don’t stir it, the whole pan of soup eventually heats up. Use the principle of convection to explain why.

Radiation

• Heat is transferred through infra-red radiation. It doesn’t involve anything. It is mostly absorbed by dark, dull objects and reflected by bright, shiny objects.

Assessment activity 2.3

1. Explain why the whole pan of soup gets hot, even if you don’t stir it. P1

2. Work in groups of 2 or 3. Produce a leaflet showing different ways we use heat transfer in the home and the work place

REMEMBER: solids transfer heat energy by conduction and fluids by convection. Radiation is light and doesn’t need a medium to transfer

through