1. Chapter 10 (briefly!)

2. Energy transfer (3 TYPES) Conduction Convection Radiation
HEAT TRANSFER
Energy transfer (3 TYPES) Conduction Convection Radiation

3. Conduction Heat transfer from one particle to the next
Particles at the warm end move faster and this then causes the next particles to move faster and so on.
In this way heat in an object travels from: the HOT end the cold end

4. Conduction cont…
Occurs when particles hitting each other and so energy is transferred.
Can happen in solids, liquids and gases
Happens best in solids-particles very close together

5. Conductors Conductors: Materials that conduct heat quickly
All metals are good conductors of heat
Pans for cooking are usually made with a copper or aluminium bottom and plastic handles (plastic is a poor conductor…you won’t get burned)

6. Insulators/poor conductors
Insulators: materials that conduct heat slowly or poorly
Glass, wood, plastic and rubber are poor conductors (good insulators)

7. Convection Convection: Heat transfer by movement of fluids
Convection Currents: heat carried by the particles.

8. Convection Currents
Hot liquids and gases expand and rise while the cooler liquid or gas falls (all caused by a difference in densities!)
2. Goes across
3. Then down
1. Hot air rises
4. And across

9. Radiation
Radiation: Transfer of heat directly from the source to the object by a wave, travelling as rays.
Heat radiation is also known as
Heat transfer by radiation does not need particles to occur and is the only way energy can be transferred across empty space
INFRA-RED RADIATION

10. Emission of Radiation (canned heat lab 2)
Hotter objects emit (give out) heat
Different surfaces emit heat at different speeds
A dull black surfaces loses energy more quickly – it is a good radiator
A bright shiny or white surface is a poor radiator
Survival kits have shiny heat blankets in them, covering in a shiny blanket reduces radiation and therefore heat loss.

11. Emitters of heat Bright shiny can Poor radiator
Dull black can Good Radiator

12. Absorption of Heat (canned heat lab 1)
Cooler objects absorb (take in) heat
Substances absorb heat at different speeds
Dull, black surfaces absorb heat quickly
Bright, shiny surfaces absorb heat slowly
In hot countries, people wear bright white clothes and paint their houses white to reduce absorption of energy from the sun.
Gas/Oil storage tanks are sprayed silver to reflect sun’s rays

13. Absorbers
Shiny, bright can Poor absorber
Dull black can Good absorber

14. Evaporation is Cooling!!
Sweating is cooling…
dogs have no sweat glands, so they pant

15. Chapter 10 bonus questions
Why is boiling a cooling process??