1. 2.4 Heat Transfers by Conduction

2. Heat Transfers by Conduction
If you have ever roasted a hot dog over a fire or tried to take something out of the oven… you would have noticed that the heat from the fire/oven has transferred to the object you are using to cook AND the food you are planning eating.

3. Conduction One way that heat transfers through matter.
The transfer of heat energy between substances that are in contact with each other.

4. Conductors
A material that allows heat energy or electricity to flow easily.
Conduction is most common in solids (less common in liquids, rare in gases).
Metals are examples of good conductors.

5. Insulator Are materials that do not allow easy transfer of heat.
The reduce the amount of heat that can transfer from a hotter object to a colder one.
Ex. Plastic, cork, and wood are good insulators ( or poor conductors of heat)

6. Conductor or Insulator?

7. 2.5 Heat Transfers by Convection and Radiation

8. Convection Another way that heat transfers through matter.
It is the flow of heat energy that involves moving liquid or gas particles.

9. Convection Currents
Are a pattern of moving liquid that involves moving liquid or gas particles when heat energy is transferred to a substance.

11. Convection currents in air
Heat transfers by convection move in only one direction:
(From an area of greater kinetic energy to one of lesser kinetic energy)
As heat transfers to air the particles EXPAND and become LESS DENSE ( close together)
Air as it is heated RISES Cooler air then moves in to take tis place near the heat source

12. Convection Currents in Air

13. Energy Efficient Windows
Old windows (storm windows) used to let all of the heat from your house escape to the outdoors in the winter. In the summer they would let all of the heat on a cold day into your house.
Today we have developed energy efficient windows. Energy efficient windows are designed to decrease heat transfer
Some windows even have a gas called argon or krypton in between the window panes ( they are better insulators than air)

14. Radiation The flow of energy in the form of invisible waves.
Radiation is different from convection and conduction because: It does not rely on the movement of particles to transfer heat energy. EX. The Sun
The energy that is transferred from its source by radiation is called Radiant Energy.

17. Radiation Heat is only one type of radiant energy.
It is transferred by invisible waves called infrared waves.
When the invisible radiant energy comes in contact with an object the object increasers in kinetic energy…. What happens to the object?
Ex. A Car on a hot day
Ex. Dark vs. Light clothing on a hot day

19. Reflect or Absorb? Matter can reflect or absorb radiant energy.
Objects that are shiny and light coloured are good reflectors of radiant energy.
Objects that are dull and dark coloured are good at absorbing radiant energy.