1. Heat Transfer Conduction, Convection and Radiation

2. How is Heat Transferred?
There are THREE ways heat can move.
Conduction
Convection
Radiation

3. Thermal Energy Transfer
Thermal energy transfer is heat moving from a warmer object to a cooler object. This is known as thermal energy transfer.

4. CONDUCTION
Heat is transferred from one particle of matter to another in an object without the movement of the object.
Conduction = CONTACT

5. Conduction
When you heat a metal strip at one end, the heat travels to the other end.
As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this?
Conduction

6. Metals are different
The outer e______ of metal atoms drift, and are free to move.
lectrons
When the metal is heated, this ‘sea of electrons’ gain k_____ energy and transfer it throughout the metal.
inetic
Insulators, such as w___ and p____, do not have this ‘sea of electrons’ which is why they do not conduct heat as well as metals.
ood
lastic

7. Why does metal feel colder than wood, if they are both at the same temperature?
Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

8. Have you ever…
Touched a metal spoon sitting in a pan of boiling water only to be surprised by HOW hot it is??
Think back to what you know about metals and nonmetals. What conducts heat better, metal or nonmetal? Why?

9. EXAMPLE OF CONDUCTION
A piece of cheese melts as heat is transferred from the meat to the cheese (Contact)

10. CONVECTION
Convection is the movement that transfers heat within fluids and air (gas)
Heat is transferred by currents within the fluid or gas
Convection = VENTS (through air and liquid particles)
Convection moves in
a circular pattern

11. The particles spread out and become less dense.
Convection
What happens to the particles in a liquid or a gas when you heat them?
The particles spread out and become less dense.
This effects fluid movement.
What is a fluid?
A liquid or gas.

12. Fluid movement
Cooler, more d____, fluids sink through w_____, less dense fluids.
ense
armer
In effect, warmer liquids and gases r___ up.
ise
Cooler liquids and gases s___.
ink

13. Water movement Cools at the surface Convection current Hot water rises
Cooler water sinks

14. Where is the freezer compartment put in a fridge?
Cold air sinks
Where is the freezer compartment put in a fridge?
Freezer compartment
It is warmer at the bottom, so this warmer air rises and a convection current is set up.
It is put at the top, because cool air sinks, so it cools the food on the way down.

15. Why is it windy at the seaside?

16. Examples of Convection:
Have you ever noticed that the air near the ceiling is warmer than the air near the floor? Or that water in a pool is cooler at the deep end?
Examples: air movement in a home, pot of heating water.
Pick one of these examples and draw the circular pattern in your notes.
When the water at the bottom of a pot is heated, its particles move faster, and they also move farther apart. As a result, the heated water becomes less dense. A less dense fluid will float on top of a more dense one. Therefore, the heated water rises in the pot. The surrounding cooler water flows into its place.
This flow creates the circular motion as seen on the next page, which is known as convection currents.

17. Explaining Convection
Convection currents cause the cooler breezes you experience by a large body of water.
These currents also cause the movement of magma within the earth.

18. RADIATION Radiation is the transfer of energy by electromagnetic waves
Radiation does NOT require matter to transfer thermal energy
Radiation = Radiates (heat escaping the sun)

19. Radiation May Come From Other Sources
Have you ever sat too close to a campfire while cooking marshmallows? You’re enjoying the warmth ….. only to notice that your skin is really warm?

20. The third method of heat transfer
How does heat energy get from the Sun to the Earth?
There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection.
RADIATION ?

21. Radiation travels in straight lines True/False
Radiation can travel through a vacuum
Radiation requires particles to travel
Radiation travels at the speed of light

22. Emission experiment Shiny metal Dull metal Dull black Shiny black
Four containers were filled with warm water. Which container would have the warmest water after ten minutes?
Shiny metal
Dull metal
Dull black
Shiny black
The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.
shiny metal
radiation
dull black
emitting

23. Absorption experiment
Four containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes?
Shiny metal
Dull metal
Dull black
Shiny black
The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best. The _________ container would be the coolest because it is the poorest at __________ heat radiation.
dull black
radiation
shiny metal
Absorbing

24. Examples of RADIATION
Fire
Heat Lamps
Sun

25. 1. Which of the following is not a method of heat transfer?
A. Radiation
B. Insulation
C. Conduction
D. Convection

26. 2. In which of the following are the particles closest together?
A. Solid
B. Liquid
C. Gas
D. Fluid

27. 3. How does heat energy reach the Earth from the Sun?
A. Radiation
B. Conduction
C. Convection
D. Insulation

28. 4. Which is the best surface for reflecting heat radiation?
A. Shiny white
B. Dull white
C. Shiny black
D. Dull black

29. 5. Which is the best surface for absorbing heat radiation?
A. Shiny white
B. Dull white
C. Shiny black
D. Dull black