1. Topic: Heat and Temperature.
Chapter 8

2. Learning Outcomes Lesson 1 Lesson 2 Lesson 3
1) Understand that heat is a form of energy and that it can be converted into other forms of energy.
2) Investigate and describe the expansion of solids, liquids and gases when heated, and contraction when cooled.
3) Demonstrate the expansion of water on freezing.
Lesson 2
1) Explain the difference between heat and temperature.
2) Explain the 3 methods of heat transfer
3) Carry out simple experiments to show the transfer of heat energy by conduction, convection and radiation
Lesson 3
1) Identify good and bad conductors/insulators of heat.
2) Understand the changes of state
3) Explain latent heat.
4) Plot a heat curve and explain the shape of the curve in terms of latent heat
5) Investigate the effect of pressure on the boiling point of water

3. Heat
Chapter 8
Chapter 8
Heat

4. Lesson 1
1) Understand that heat is a form of energy and that it can be converted into other forms of energy.
2) Investigate and describe the expansion of solids, liquids and gases when heated, and contraction when cooled.
3) Demonstrate the expansion of water on freezing.

5. Heat is a form of energy What is energy?
Energy is the ability to do work
Heat is a form of energy
Heat has the ability to do work
E.G. It helps flowers to grow

6. Heat is a form of energy Heat is a form of energy
Heat can not be created or destroyed it can only be converted from one form to another
e.g. A runner:
His kinetic (moving) energy is converted into heat energy as he gets hot and
starts to perspire.

7. Heat is a form of energy Heat energy can be converted to other forms
Volcano
Heat Energy
Kinetic Energy

8. Expansion Solids, Liquids and gases all expand when heated.
On cooling they contract or get smaller

9. Expansion Liquids expand when heated. Water level rises Apply Heat
What do you think will happen?
This is a mandatory experiment.
Bunsen Burner
Coloured water

10. Expansion of Liquids
A practical use of expansion of liquids is thermometers.
Examples include mercury and alcohol thermometers.
When placed in something hot the liquid rises up the tube.
Note
rise
Practical example of expansion of liquids.
Mercury
Hot Liquid

11. Expansion of Solids Ball and ring apparatus
This is a mandatory experiment. Be careful with the rod as it becomes very hot on heating.
The ball does not fit through the ring at room temperature

12. Expansion of Solids
Heat the ring using a bunsen burner

13. Expansion of Solids What do you think will happen now????
When the ring was heated it expanded.
The ball now fits through the ring proving the expansion.

14. Expansion of Gases Air Bubbles The air in the flask is heated.
This is a mandatory experiment.
The air in the flask is heated.
The air expands producing the bubbles

15. Expansion of Gases Air Bubbles
What would happen if I stopped heating the flask?

16. Expansion of Gases Air Answer: Contraction
Liquid gets sucked up the tube

17. Water is an exception !
Freeze
Ice
If you take a glass and note the level of water in it
you will find, that on freezing
the volume of the water expands
Fact: Below 4°C water starts to expand

18. Lesson 2 1) Explain the difference between heat and temperature.
2) Explain the 3 methods of heat transfer
3) Carry out simple experiments to show the transfer of heat energy by conduction, convection and radiation
4) Know that all hot bodies radiate heat.

19. Temperature and Heat Temperature == Heat
Heat is a form of energy and is measured in joules.
Temperature is a measure of how hot something is.
Thermometers are used to measure temperature.
Normally thermometers contain alcohol or mercury.
Liquid expands up the capillary tube when in contact with something hot

20. Heat Transfer What are they? There are 3 methods of heat transfer:
1) Conduction
What are they?
2) Convection
3) Radiation

21. Conduction

22. Conduction Consider a poker in a fire.
If left for a long time the handle will become hot even though the handle is not in contact with the fire.
Heat transferred in this way is known as conduction.

23. Conduction Definition:
Conduction is the transfer of heat through a solid without the
particles of the solid moving out of position.
I would spend time explaining the animated diagram emphasising that the particles are staying in the same position while the heat is being transferred.

24. To Show that water is a poor conductor of heat
This apparatus is used to show that water is a poor conductor of heat.
The water at the top of the boiling tube boils, though the ice at the bottom does not even melt.
Therefore water is a poor conductor of heat. Heat does not pass quickly from the top of the liquid to the bottom.
This is a mandatory experiment. Only point one would be displayed with diagram until such time as the students have carried out the experiment. Afterwards I would pose a thought provoking question: Why could I not just let the ice cube float on the top and heat the bottom of the boiling tube? I would ask them to think about it and see if they could come up with an answer after learning about convection currents.

25. Conductometer
A conductometer is an instrument consisting of a heat proof handle
Together with 5 metal rods made of
aluminium, brass, copper, nickel and steel.
The metal rods are of equal length and cross sectional area.

26. To show Transfer of Different Metals using a Conductometer
Stick a cent to the end of each
rod using some wax.
Heat the centre of the rod.
The cents will drop from the
rods one by one.
This show that the heat has been
conducted along the rods.
It also shows that different metals
conduct at different rates.
This is a mandatory experiment.
A conductometer can be bought quite easily these days on the net. I think its less messy than the bath with all the rods hanging out of it. One needs to be careful though. The pennies should drop in less than 5 minutes. Beyond that time there is a danger that the rods themselves might fall off!

27. Convection

28. Convection Convection currents occur in fluids i.e. liquids or gases.
The water directly above the flame gets hot, becomes less dense and rises.
Cooler water (which is more dense) falls from the top to the bottom where it in turn gets heated.

29. Convection Definition
Convection is the transfer of heat through a liquid or gas when the particles of the liquid or gas move and carry the heat with them.
A kettle of water boils using convection currents.

30. To Show Convection Currents in Water Apparatus:
Another mandatory experiment. Only a very gentle heat required so that one can see the formation of convection currents. Some books suggest using a candle.
Using a Bunsen burning heat a crystal with a VERY GENTLE
heat and observe what happens

31. To Show Convection Currents in Air Smouldering rope Smoke Box
Mandatory experiment again- pretty straight forward.
Smoke Box

32. Radiation

33. Radiation Consider a grill cooking sausages.
Air is a very poor conductor.
In convection, heated particles rise upwards not downwards.
So how do the sausages receive heat?
Radiation!!!

34. Radiation
Definition
Radiation is the transfer of heat from a hot object without the need for a medium.
Radiation
The earth is heated by
radiation rays from the
sun.

35. To Investigate the Transfer of Heat by Radiation
This is a mandatory experiment. Other sources of heat could be used instead of the bulb. Allow the students to note their observations and see if they can come up with the conclusion before you confirm it.
What do you observe?
Dark coloured or dull surfaces both emit and absorb radiation better than light coloured or shiny surfaces.

36. Radiation All hot bodies radiate heat.
This is one of the learning outcomes. I would emphasis that all hot bodies radiate heat. I use a pic of a fire because its obvious but mention other things e.g. the human body radiates heat.

37. Lesson 3 1) Identify good and bad conductors/insulators of heat.
2) Understand the changes of state
3) Explain latent heat.
4) Plot a heat curve and explain the shape of the curve in terms of latent heat
5) Investigate the effect of pressure on the boiling point of water

38. Insulators An insulator is a substance that does not allow heat to
flow through it easily
Examples of insulators:
Insulators- I would probably talk a bit about insulating your home and how trapped air is the insulator used in double glazing.
Curtains
Wood
Fibreglass

39. Conductors A conductor is a substance that allows heat to flow
through it easily.
Examples include:
Metals are the best conductors.
Silver
Gold

40. Changes of State There are 3 states of matter: Solids Liquids Gas Gas
This is revision. They should have come across this in early chapters of chemistry. I do a recap to help with the latent heat eplanation.

41. Changes of State Apply heat melting evaporating Solid Liquid Gas
freezing
condensation
Remove heat

42. Latent Heat
Latent Heat is the heat taken in or given out when a substance
is changing state without a change in temperature.
1) If ice is heated its temp rises until it reaches 0°C.
2) A change of state occurs; solid → liquid, so no rise in temperature is seen.
3) When all ice is melted its temp starts to rise again.
4) At 100 °C another change of state occurs. Liquid → Vapour so no rise in temp is seen.
5) When all the liquid has evaporated the temp starts to rise again.
Temp
(°C) 4 5
100 3 2 1
Time (min)

43. Latent Heat
So where on the curve would you label the latent heat areas?
Where there is no rise in temperature!
Time
(min)
100
Latent Heat
Temperature
deg C

44. To Investigate the Effect of Pressure on the Boiling Point of Water
This is not a mandatory experiment but its on the syllabus. It could be carried out as a teacher demonstration.
Apparatus required

45. Assessment Section A Q1 Heat is a form of _______.
Q2 The units of heat are ________.
Q3 Solids, liquids and gases _______ when heated and ________ when cooled.
Q4 Water is an exception to this rule as it starts to ______ below 4 °C.
Q5 Define temperature. What are its units?
Q6 On what principle are thermometers based?
The assessment here can be printed up and handed out to the students or it can be carried out orally.

46. Assessment
Q7 Conduction is the transfer of heat through a _______ without movement of the __________.
Q8 Convection is the transfer of _______ through a __________ or a ________.
Q9 What is Radiation?
Q10 A dull black surface _______ heat better than a bright shiny surface.
Q11 All hot bodies _________ heat.
Q12 What is an insulator? Name 2 examples.

47. Assessment Q13 What is a conductor? Name 2 examples.
Q14 List the three states of matter.
Q15 Latent heat is the heat ______ in or given out when a
substance is changing ______ .
Q16 When latent heat is taking place there is _______change in temperature.
Q17 Increasing the pressure on water __________ its boiling point.

48. Assessment
Section B
Q1 What is the following instrument and what is it used for?

49. Assessment
Q2 What is the following instrument and what is it used for?

50. Assessment
Q3 Draw arrows in the saucepan of water to indicate the direction of the convection currents.

51. Assessment Wool Trapped Air Silver Fibreglass Gold Mercury
Q4 Indicate which of the following is a good conductor
or a good insulator.
Wool
Trapped Air
Silver
Fibreglass
Gold
Mercury

52. Assessment
Q5 The graph shows the rise in temperature of water. Heat is applied to the water continuously.
Explain why there is no rise in temperature at point “A” and “B”.
____________________________
Temp
Deg C
Time
(min)
100 B A

53. Bibliography
A voyage of discovery (Dorgan, Kennedy and Walsh)