1. Section 2: Transferring Thermal Energy
Chapter 6: Thermal Energy

2. Warm-up: What does it mean to be a good conductor?
What types of materials are the best conductors?

3. Learning Goals
Compare the transfer of heat energy through conduction, convection, and radiation.
Compare and contrast conductors and insulators.
Explain how insulators are used to control the transfer of thermal energy.

4. Transferring Thermal Energy
There are 3 ways that thermal energy is transferred from place to place:
Conduction
Convection
Radiation

5. Conduction
Conduction: transfer of thermal energy by collisions between particles in matter
Think of a metal spoon being heated by a flame.

6. Conduction
Kinetic energy of the particles close to the flame increases.
Those particles collide with the particles close to them and thermal energy is transferred.

9. Conduction
Conduction occurs when thermal energy is transferred from place to place without the transfer of matter!

10. Heat Conductors
Heat moves fastest by conduction in solids.

11. Heat Conductors
Heat moves a little slower by conduction in liquids.

12. Heat Conductors
Heat moves the slowest by conduction in gases because the particles are so far apart.

13. Heat Conductors
The best conductors of heat are metals because their electrons flow freely through the metal.
Silver, copper, and aluminum are among the best conductors of heat.

14. Convection
Convection: transfer of thermal energy in a fluid (liquid or gas) by the movement of warmer and cooler fluid from place to place.

15. Convection
More energetic particles collide with less energetic particles and transfer thermal energy.
More energetic particles move faster from place to place.

16. Convection – the lava lamp
Oil is cool and dense and sits on the bottom of the lamp.
As it warms, the oil expands and becomes less dense than the surrounding fluid.

17. Convection – the lava lamp
The oil then rises and loses heat to the surrounding fluid.
It becomes dense again and sinks.

18. Radiation Radiation: transfer of energy by electromagnetic waves
Energy transferred by radiation is called radiant energy.

19. Radiation
When you stand near a fire to warm your hands, you are warming them using radiation.

22. Insulators Insulator: material that slows down heat transfer
Gases are usually much better insulators than solids or liquids.
Conduct heat poorly since particles are far apart.

23. Insulators
Examples: fleece jacket and thermos

24. Check-In:
Would plastic foam (which contains pockets of air) be a good insulator or good conductor? Explain why.