1. Methods of Heat Transfer
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Methods of Heat Transfer

2. Connector Can you explain why:-
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Can you explain why:-
Freezers in supermarkets are often left open to the air. Explain why the food does not melt easily.
Explain why an ice cube floating at the top of a drink will cool all of the drink.

3. Why does metal feel colder than wood, if they are both at the same temperature?
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4. Conduction Demos Demonstrate Conduction Rods and lead a discussion
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Demonstrate Conduction Rods and lead a discussion

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. Conduction in non-metals

7. Conduction in metals
Conduction in metals

8. Why are Metals better conductors than non metals?
Higher Only

9. 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

10. 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.

11. Words – vibrations, electrons, solid, heated, better
Conduction
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Conduction is all about when heat is transferred through a _________. The heat is passed on by ___________ in the molecules. These vibrations get BIGGER when the solid has more ENERGY (i.e. when it is being __________).
Metals are _______ conductors than non-metals. This is because the heat is carried by free ________ that can carry the energy around the metal and give it to other electrons and ions.
Heating a non-metal
Heating a metal
Words – vibrations, electrons, solid, heated, better

12. What is common about Conduction and Convection?
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What is common about Conduction and Convection?
Discuss with the person next to you…

13. What is common about Conduction and Convection?
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What is common about Conduction and Convection?
Both Conduction and Convection require matter to travel through.

14. So how do we get our heat energy from Space?
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So how do we get our heat energy from Space?

15. 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 ?
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16. All hot objects emit INFRA RED Radiation!
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All hot objects emit INFRA RED Radiation!
Radiation Demo – Using an IR Sensor or a IR Thermometer pour some hot water in a cup.

17. What is Infra Red Radiation?
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IR Radiation is a type of light which is invisible to our eyes.
Since it is light what are some of the properties of IR Radiation?
It travels at the speed of light (3x108 m/s)
It travels in straight lines
It can be reflected
It can be absorbed

18. Modelling Heat loss
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You have now learnt about three different types of heat loss. They are:-
Conduction
Convection
Radiation
We are now going to model this heat loss.
In our model you will behave like particles of matter and the heat energy will be represented by tennis balls.

19. Modelling Conduction
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Give students instructions to correctly model conduction.
Ask students how they will now represent convection and radiation.
Lead a discussion and then get students to model.

20. Modelling Heat Loss
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Conduction – Students pass tennis balls from one part of the class room to another
Convection – Students run from one part of the class room to another
Radiation – Students throw tennis balls from one part of the class room to another

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What kind of materials are good absorbers and emitters of Infra Red Radiation?
Can be investigated in a separate lesson. Get students to plan the investigation with variables etc.

22. Leslie’s Cube Demo
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Watch the demo. The demo shows how different coloured objects EMIT Infra Red Radiation.
Which object do you think will be the best emitter?
What do you notice?
What can you conclude?

23. Investigating thermal emission
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Teacher notes
This virtual experiment uses a Leslie’s cube to investigate the emissions of heat radiation from different surfaces. It could be use as a precursor to running the practical in the lab or as a revision exercise. When using this activity, it should be made clear that the water inside the cube and the initial temperature of each side is the same in each experiment. The thermopile measures the amount of heat radiation emitted by the surface, which is then recorded in the table.

24. Emitting Radiation
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Emitting Radiation

25. Dark Matt Coloured Objects are best at emitting Infra Red Radiation.
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Dark Matt Coloured Objects are best at emitting Infra Red Radiation.
White or shiny objects are worst emitters of Infra Red Radiation.
This is because they reflect the radiation instead.

26. Investigating Radiation
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Plan an experiment to investigate which type of material is best at ABSORBING Infra Red Radiation.
The materials to be used are:-
White Paper
Black Paper
Aluminium Foil

27. Temperature in each boiling tube / 0C
Radiation Practical
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Time / min
Temperature in each boiling tube / 0C
Black
White
Aluminium Foil 1 2 3 4 5 6 7 8 9 10

28. Investigating thermal absorption
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Teacher notes
This virtual experiment investigates the ability of different surfaces to absorb heat. It could be use as a precursor to running the practical in the lab or as a revision exercise. To extend the activity, students could be asked to consider which variables need to be controlled to make this experiment fair and accurate.

29. Conclusion What do your results show you? Form a conclusion.
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What do your results show you?
Form a conclusion.

30. Absorption of Radiation
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Absorption of Radiation

31. Conclusion
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Dark, Matt Colours are the ______ absorbers of Infra Red Radiation.
Light Shiny objects (Aluminium Foil) are the _______ absorbers of Infra Red Radiation. This is because they ______ them.

32. Radiation
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Radiation is when heat moves around in electromagnetic _________ like light does. Any hot object will emit heat radiation – the hotter it is, the more radiation it emits. This type of radiation is called __________, and too much of it will cause _________. Dark, matt colours will absorb AND emit the _____ infra-red radiation, and light, shiny colours will ________ it.
The main difference with radiation is that conduction and convection could ONLY happen in solids, liquids or gases, whereas radiation will happen through an _____ _____. This is just as well, as otherwise we wouldn’t be able to get any heat from the ___.
Words – sun, reflect, infra-red, waves, most, empty space, sunburn
Anything HOT emits HEAT RADIATION – the hotter it is, the more infra red radiation it emits

33. Some examples of radiation
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“Thermograms”

34. Some examples of radiation
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Some examples of radiation

35. Plenary
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1) Explain how and where all 3 processes of heat transfer happen in a bonfire
2) By considering how a Thermos Flask is built explain how it manages to keep hot drinks hot and cold drinks cold.