1. Understanding Heat Transfer: Conduction, Convection and Radiation

2. Question
If a cup of coffee and an ice cream cone were left on the table in this room what would happen to them? Why?
The cup of coffee will cool until it reaches room temperature. The ice cone will melt and then the liquid will cool to room temperature.

3. What is Heat?
This is the movement of thermal energy from a substance at a higher temperature to another at a lower temperature.

4. Heat is the actual energy…
Heat vs. Temperature
Heat is the actual energy…
Temperature is the measure of average kinetic energy of particles in a substance.

5. Heat is NOT Temperature

6. Heat Transfer Heat always moves from a warmer place to a cooler place.
Hot objects in a cooler room will cool to room temperature.
Cold objects in a warmer room will heat up to room temperature.

7. Conduction Convection Radiation Heat Transfer Methods
Heat transfers in three ways:
Conduction
Convection
Radiation

8. Conduction
Conduction heat transfer is the flowing of heat energy from a high-temperature object to a lower-temperature object. Must have contact (touch)

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

10. 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?

11. 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

12. 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

13. 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.

14. Convection
Convection takes place when heated molecules move from one place to another, taking the heat with them. Convection is common in both the atmosphere, as well as in the oceans. Convection = VENTS Convection is the primary way that heat moves through gases and liquids.

15. Convection

16. 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

17. 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.
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.

18. 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.

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

20. 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.

21. Why is it windy at the seaside?

22. Radiation

23. 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 ?

24. 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)

25. Examples of RADIATION
Fire
Heat Lamps
Sun

26. Radiation Radiation travels in straight lines True/False
Radiation requires particles to travel
Radiation travels at the speed of light

27. Radiation The transfer of energy by electromagnetic waves. Examples:
Sun
Fire
Light bulb

28. Radiation question Why are houses painted white in hot countries?
White reflects heat radiation and keeps the house cooler.

29. Example of Conduction
Think of a metal spoon in a pot of water being heated.
The fast-moving particles of the fire collide with the slow-moving particles of the cool pot.
Because of these collisions, the slower particles move faster and heat is transferred.
Then the particles of the pot collide with the particles in the water, which collide with the particles at one end of the spoon.
As the particles move faster, the metal spoon gets hotter. This process of conduction is repeated all along the metal until the entire spoon is hot.
Have an example sitting in front on the lab table (doesn’t need to be on); a visual.

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

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

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

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

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

36. To Make Foldable: Conduction Convection Radiation Heat Transfer
1. On the short side of the paper, fold it down an inch.
2. Now fold it in half, hamburger style.
3. Now fold it in 1/3.
Outside of Foldable
Inside of Foldable
Conduction
Convection
Radiation
Examples
Definition
Heat Transfer

37. 3 Ways Energy (Heat) is Transferred
*Transfer of heat (energy) that happens when molecules bump into each other
*Objects must be touching
*”Conduction is touchin’”
*Transferred in rays or waves
*Energy from the Sun warms the Earth
*Transfer of heat by the flow of material
*In warm air, the molecules move apart, so it is less dense and rises
*In cooler air, the molecules move closer together, so it is more dense and sinks
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