1. Heat a form of Energy By
Neil Bronks

2. Temperature Measure of how hot or cold something is
This is the science version of shouting at a waiter in Ibiza (it really does not help but it’s the best we have).

3. Thermometers Fixed Point Thermometric Property Scale
Three things that make up a thermometer
Fixed Point
Usually the
boiling point
and melting points
of water
Scale
Divisions between
the fixed points
Thermometric
Property
Something
that varies
Measurably with
temperature

4. Different Thermometers
Thermocouple
Junction emf
Platinum Wire
Resistance
CVGT
Pressure
Emf
Temp R
Temp
Pressure
Temp
The only linear thermometric property is the CVG.
All the others must be calibrated to the CVG

5. Show them the CVGT

6. Different Temperatures
Thermocouple
Junction emf
Emf
Temp
Platinum Wire
Resistance R
Temp
Because the different thermometric properties react differently at the same temperature

7. Different Thermometers
Thermocouple
Junction emf
Platinum Wire
Resistance
CVGT
Pressure
Emf
Temp R
Temp
Pressure
Temp
CVG is a standard thermometer and is used to calibrate the others

8. CALIBRATION CURVE OF A THERMOMETER USING THE LABORATORY MERCURY THERMOMETER AS A STANDARD
Alcohol thermometer uncalibrated
Mercury thermometer
Boiling tube
Water
Glycerol
Heat source

9. Temperature in Celsius43 23
Length in cm

10. Fixed Points – Alternative to Calibration Graph
Use BP and MP of water
Divide up gap between into 100 division scale

11. Kelvin and Celsius
Add 273 to Celsius and you get the temperature in Kelvin
Lowest possible temperature is -273oC
This is zero Kelvin OK

12. Calibration Movie

13. 2003 Question 12 (b) [Higher Level]
What is the difference between heat and temperature?
The emf of a thermocouple can be used as a thermometric property. Explain the underlined terms.
Name a thermometric property other than emf.
Explain why it is necessary to have a standard thermometer.

14. H/W
LC Ord 2007 Q 3
And LC Ord 2005 Q12(a)

15. Thermometer Challenge?

16. Electro-magnetic wave
Heat Transfer
Convection
Hot air
rising
carrying
the
heat up
with it.
Conduction
-Transfer by
vibrations
Radiation
-Transfer by
Electro-magnetic wave

17. Conduction
In a solid every atom is physically bonded to its neighbours in some way.
If heat energy is supplied to one part of a solid, the vibration travels through the solid.
Conduction is the transfer of energy through matter from particle to particle. It is the transfer and distribution of heat energy from atom to atom within a substance.

18. Practical Conduction
A spoon in a cup of hot soup becomes warmer because the heat from the soup is conducted along the spoon. Conduction is most effective in solids
It is also why stone and metals appear cold. They are just good conductors.
Chilly

19. Water as a Poor Conductor
Test Tube of water
The ice does not melt as the water is a terrible conductor and convection only works up.
HEAT
Metal Gauze
ICE

20. U-Value
U- Value (or Heat transmittance) is a measure of how good an insulator something is. A good insulator has a low U-value.
Defined as the rate of heat energy transfer through 1m2 where the temperature difference is 1k
Q/t
(θ+1)0C
θ0C
1m2

21. Convection
Most houses have radiators to heat their rooms. This is a bad name for them - as they give off heat mainly by convection!
The air expands and is less dense so it rises
It cools and falls (So hot fluids rise not heat)
CONVECTION CURRENT

22. Domestic Heating System

23. Sea Breezes
Day – On Shore
HOT LAND
WARM SEA

24. Sea Breeze Night
Night – Off Shore
COLD LAND
WARM SEA

25. Radiation
The transfer of heat in the form of an electro-magnetic wave.
Only form of heat that can travel through a vacuum

26. A silver or white body holds heat in so to reduce heat loss we use silver or white.
Black bodies radiate more heat so we paint things black when we want to lose heat.

27. Vacuum Flask

28. Solar Constant
The average amount of solar energy falling on 1 square meter of atmosphere per second
About 1.35kWm-2
At the poles the same amount of energy from the sun is spread over a much larger surface area.
Than the equator

29. H/W
LC Ord 2006 Q 7
LC Ord 2004 Q7

30. Heating a solid
Temperature
Boiling point
Melting point
Time

31. Heating a solid Boiling point Heat raises temperature Energy=mcΔθ
Latent Heat Only
Energy=ml
Liquid
Boiling
Melting point
Solid
Melting
Time

32. The Refrigerator Liquid boils and takes in Latent Heat from the food
Gas
Gas turns back into a liquid giving out heat
Compressor

33. Storage Heater
Uses cheap night time electricity to heat up bricks with large heat capacity
Release slowly during the day

34. Heat Capacity
Amount of heat to raise temperature of this tank by 1 degree Celsius
Specific Heat Capacity-Amount of heat to raise temperature of 1kg by 1oC

35. Heat Capacity
Amount of heat to raise temperature of this kettle by 1 degree Celsius (Different from the tank)
Specific Heat Capacity-Amount of heat to raise temperature of 1kg by 1oC(Same as always)

36. Heating Up Heat that raises temperature Energy Supplied=Q=mcΔθ
Where m = mass of body
Δθ=Change in Temperature
c = Specific Heat Capacity
Amount of heat energy
to raise
1kg by 1k

37. (Where c=390 j/kg/kelvin)
Example
How much energy does it take to heat up 2kg of copper by 30 degrees?
(Where c=390 j/kg/kelvin)
As Q=mc∆
Q= 2 x 390 x 30
= Joules

38. (Where c=4200 j/kg/kelvin)
Example
How much energy does it take to heat up 500ml of water from 20oC to B.P.?
(Where c=4200 j/kg/kelvin)
As Q=mc∆
Q= 0.5 x 4200 x 80
= Joules

39. Class Challenge
Water falls over a waterfall in perfect conditions (surrounded by spherical chickens in a vacuum) at the bottom it is 1 degree hotter than the top. How high is the waterfall?
Take g=9.8 m/s2 and c=4200 j/kg/k

40. Power If this takes 5 mins how much power is needed?
Power = Work done/ Time
= /300s
= Watts

41. (b) [Ordinary Level]
An electric kettle is filled with 500 g of water and is initially at a temperature of 15 0C.
The kettle has a power rating of 2 kW.
Calculate the energy required to raise the temperature of the water to 100 0C.
How much energy is supplied by the kettle every second?
How long will it take the kettle to heat the water to 100 0C?
Name a suitable material for the handle of the kettle. Justify your answer.
(specific heat capacity of water = 4180 J Kg−1 K−1)

42. Classwork
LC Ord Q 7

43. Heat that changes state without changing temperature
Latent Heat
Heat that changes state without changing temperature
Energy Supplied=ml
Where m = mass of body
l = Specific Latent Heat
Amount of heat energy
to change state of1kg
without changing temp.

44. Latent Heat
Heat-Amount of heat to change state of water in kettle without changing temperature
Specific Latent Heat-Amount of heat to change state of 1kg of water without changing temperature

45. A lot more than heating it up!
Example
How much energy does it take to turn 2kg of copper into a liquid?
(latent heat of fusion of Copper l= j/kg)
As Q=ml
Q= 2 x
= Joules
A lot more than heating it up!

46. Frozen Wine
A litre of wine at 20 0C. is left in the freezer by accident. It freezes and reduces to C. How much energy does this take?
3 stages
Cools to zero
Freezes
Cools to -10 0C.

47. Wine has c=4000j/kg/kelvin, =1kg/litre
Stage 1
Wine has c=4000j/kg/kelvin, =1kg/litre
Using Q=mc
=  V c 
=1x1x4000x20
=80000joules

48. Wine has latent heat of fussion l = 300000j/kg
Stage 2
Wine has latent heat of fussion l = j/kg
Using Q=ml
=  V l
=1x1x300000
=300000joules

49. Frozen Wine has c=3000j/kg/kelvin, =1kg/litre
Stage 3
Frozen Wine has c=3000j/kg/kelvin, =1kg/litre
Using Q=mc
=  V c 
=1x1x3000x10
=30000joules
Different
from liquid

50. Total
= = joules
How long will this take in a 100Watt fridge?
100w = 100 joules/second
Time = /100 = 4100 seconds
= 4100/3600 = 1.13 hours

51. 2011 Question 7 (a) [Higher Level]
When making a hot drink, steam at 100 °C is added to 160 g of milk at 20 °C.
If the final temperature of the drink is to be 70 °C, what mass of steam should be added?
You may ignore energy losses to the surroundings.
A metal spoon, with an initial temperature of 20 °C, is then placed in the hot drink, causing the temperature of the hot drink to drop to 68 °C.
What is the heat capacity of the spoon?
You may ignore other possible heat transfers.
(cmilk = 3.90 × 103 J kg–1 K–1, cwater = 4.18 × 103 J kg–1 K–1, chot drink = 4.05 × 103 J kg–1 K–1
specific latent heat of vaporisation of water = 2.34 × 106 J kg–1)

52. H/W
Higher level
2005 Q2

53. Temperature of a kilogram of ice and a kilogram of boiling water?
A kilogram of ice at 0oC and a kilogram (liter) of boiling water at 100oC are mixed together in a thermally insulated tank. What is the temperature of the water in the tank after the contents have reached equilibrium?

54. MEASUREMENT OF THE SPECIFIC HEAT CAPACITY OF A METAL BY AN ELECTRICAL METHOD
12 V a.c. Power supply
Joule meter
10°C
350 J
Heating coil
Glycerol
Metal block
Lagging

55. Energy supplied electrically = Energy gained by metal block
1.     Find the mass of the metal block m.
2.    Set up the apparatus as shown in the diagram.
3.    Record the initial temperature θ1 of the metal block.
4.    Zero the joule meter and allow current to flow until there is a temperature rise of 10 C.
6.    Switch off the power supply, allow time for the heat energy to spread throughout the metal block and record the highest temperature θ2.
8.    Record the final joule meter reading Q.
Energy supplied electrically = Energy gained by metal block
Q = mc (θ2 – θ1)

56. MEASUREMENT OF SPECIFIC HEAT CAPACITY OF WATER BY AN ELECTRICAL METHOD
12 V a.c. Power supply
10°C
Joule meter
Digital
thermometer
Cover
350 J
Water
Lagging
Calorimeter
Heating coil

57. 1. Find the mass of the calorimeter mcal.
2.    Find the mass of the calorimeter plus the water m1. Hence the mass of the water mw is m1 – mcal.
3.    Set up the apparatus as shown. Record the initial temperature θ1.
4.    Plug in the joule meter , switch it on and zero it.
5.    Switch on the power supply and allow current to flow until a temperature rise of 10 C has been achieved.
6.    Switch off the power supply, stir the water well and record the highest temperature θ2. Hence the rise in temperature is θ2 – θ1.
7.    Record the final joule meter reading Q.

58. Electrical energy supplied = energy gained by (water +calorimeter)
Q = mwcw mcalccal.
Precautions 1/. Lagging
2/. Cool water slightly so final temperature not far from room temperature.

59. MEASUREMENT OF THE SPECIFIC HEAT CAPACITY OF A METAL OR WATER BY A MECHANICAL METHOD
Cotton wool
10°C
Boiling tube
Water
Digital
thermometer
Copper rivets
Heat source
Water
Lagging
Calorimeter

60. 1. Place some copper rivets in a boiling tube
1.      Place some copper rivets in a boiling tube. Fill a beaker with water and place the boiling tube in it.
2.    Heat the beaker until the water boils. Allow boiling for a further five minutes to ensure that the copper pieces are 100° C.
3.    Find the mass of the copper calorimeter mcal.
4.    Fill the calorimeter, one quarter full with cold water. Find the combined mass of the calorimeter and water m1.
5.    Record the initial temperature of the calorimeter plus water θ1. Place in lagging
6.    Quickly add the hot copper rivets to the calorimeter, without splashing.
7.    Stir the water and record the highest temperature θ2.
8.    Find the mass of the calorimeter plus water plus copper rivets m2 and hence find the mass of the rivets mco.

61. 7. Stir the water and record the highest temperature θ2.
6.    Quickly add the hot copper rivets to the calorimeter, without splashing.
7.    Stir the water and record the highest temperature θ2.
8.    Find the mass of the calorimeter plus water plus copper rivets m2 and hence find the mass of the rivets mco.
Heat lost by the Rivets=Heat gained by water and calorimeter
mco cco2 = mw cw1 + mc cc1

62. MEASUREMENT OF THE SPECIFIC LATENT HEAT OF FUSION OF ICE
Wrap ice in cloth to crush and dry.
Crushed ice
Digital
thermometer
Calorimeter
Water
Lagging

63. 1.      Place some ice cubes in a beaker of water and keep until the ice-water mixture reaches 0 °C.
2.    Find the mass of the calorimeter mcal. Surround with lagging
3.    Half fill the calorimeter with water warmed to approximately 10 °C above room temperature. Find the combined mass of the calorimeter and water m2.
4.    Record the initial temperature θ1 of the calorimeter plus water.
5.    Surround the ice cubes with kitchen paper or a cloth and crush them between wooden blocks – dry them with the kitchen paper.
6.    Add the pieces of dry crushed ice, a little at a time, to the calorimeter.
7.  Record the lowest temperature θ2 of the calorimeter.
Find the mass of the calorimeter + water + melted ice m3

64. Calculations Energy gained by ice = Energy lost by calorimeter
Calculations   Energy gained by ice = Energy lost by calorimeter energy lost by the water.   milf +micw 1= mcalcc 2+mwcw 2 milf +micw (f-0)= mcalcc (i- f) mwcw (i- f)

65. In an experiment to measure the specific latent heat of fusion of ice, warm water was placed in a copper calorimeter. Dried, melting ice was added to the warm water and the following data was recorded.
Mass of calorimeter 60.5 g
Mass of calorimeter + water g
Temperature of warm water 30.5 oC
Mass of ice 15.1 g
Temperature of water after adding ice 10.2 oC
Explain why warm water was used.
Why was dried ice used?
Why was melting ice used?
Describe how the mass of the ice was found.
What should be the approximate room temperature to minimise experimental error?
Calculate the energy lost by the calorimeter and the warm water.
Calculate the specific latent heat of fusion of ice.

66. The balancing energy losses before and after the experiment.
To remove melted ice would have already gained latent heat
Melting ice is at 0 oC.
Final mass of calorimeter + contents minus mass of calorimeter + water.
20 0C / midway between initial and final temperatures (of the water in the calorimeter)
{energy lost = } (mcΔθ )cal + (mcΔθ )warm water
= (0.0605)(390)(20.3) + (0.0583)(4200)(20.3)
= / J
{Energy gained by ice and by melted ice =}
(ml)ice + (mcΔθ )melted ice / (0.0151)l + (0.0151)(4200)(10.2) / l
(equate:) l =
l = × 105 ≈ 3.2 × 105 J kg–1

67. H/W
LC Higher 2003
Q 2

68. MEASUREMENT OF THE SPECIFIC LATENT HEAT OF VAPORISATION OF WATER
Digital
Thermometer
Steam Trap
Lagging
Water
Heat source
Calorimeter

69. 1.      Set up as shown
2.    Find the mass of the calorimeter mcal.
3.    Half fill the calorimeter with water cooled to approximately 10 °C below room temperature.
4.    Find the mass m1 of the water plus calorimeter.
5.    Record the temperature of the calorimeter + water θ1.
6.    Allow dry steam to pass into the water in the calorimeter until temperature has risen by about 20 °C.
7.    Remove the steam delivery tube from the water, taking care not to remove any water from the calorimeter in the process.
8.    Record the final temperature θ2 of the calorimeter plus water plus condensed steam.
9.    Find the mass of the calorimeter plus water plus condensed steam m2.

70. Energy lost by steam = energy gained by calorimeter +
Energy lost by steam = energy gained by calorimeter energy gained by the water   msl+msc. ∆ = mcalcc ∆ +mwcw.∆ mslv +mscw (100-f)= mcalcc (f- I) mwcw (f- I)

71. H/W
LC Ord 2003
Q 2

72. Lets do the h/w folks LC Ord 2007 Q 3 LC Ord 2005 Q 12(a)
Higher Q 2
LC Higher Q 2
LC Ord Q 2