1. Concept of Temperature
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Concept of Temperature
To feel the Hotness or coldness of an object
Different temperature scales and definitions of lower fixed point and upper fixed point
Explanation
Definition of the temperature of the body :
a measure of the average kinetic energy of each particle in that body
Absolute zero (273 C or 0 K)

2. Concept of Temperature
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Concept of Temperature
At absolute zero, the average kinetic energy of each particle is minimum.
Thermometers : graduated tool used for temperature measurement.
1. Liquid-in-glass thermometer (3 kinds)
(a) Mercury-in-glass thermometer
Photo
(b) Alcohol-in-glass thermometer
Photo
(c) Clinical thermometer
Photo

3. Concept of Temperature
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Concept of Temperature
2. Rotary thermometer
Diagram
3. Resistance thermometer
4. Thermistor thermometer
5. Thermocouple thermometer

4. Heat and Internal Energy 1
Temperature
Heat and Internal Energy 1
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Concept of Internal Energy
Unit of energy : Joule (J)
All objects are composed of small particles and every particle has both kinetic energy and potential energy.
Definition of Internal Energy :
the sum of the kinetic and potential energy of all particles in the body
Diagram
Rise in temperature means increase in internal energy.

5. Heat and Internal Energy 2
Temperature
Heat and Internal Energy 2
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Concept of Heat
Different methods to increase the temperature of the object :
1. The object is hammered violently
Diagram
2. The object is put in contact with a hotter object
Diagram
3. Energy released in chemical reactions

6. Heat and Internal Energy 3
Temperature
Heat and Internal Energy 3
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Heating Process
If a hot object is in contact with a cold object, internal energy is transferred from the hot object to the cold object. It is called the heating process.

7. Heat and Internal Energy 4
Temperature
Heat and Internal Energy 4
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Heating Capacity Specific Heat Capacity
Devices to measure the energy transferred to the heater
Photo
Experimental set-up to find the relationship between the amount of energy supplied and the rise in temperature
Diagram

8. Heat and Internal Energy 5
Temperature
Heat and Internal Energy 5
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Heating Capacity
Heat Capacity :
The energy supplied by heating process to increase the temperature of a body by 1 K (or C)
Energy needed (released)
= Heat Capacity  the temperature raised (lowered) in °C

9. Heat and Internal Energy 6
Temperature
Heat and Internal Energy 6
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Specific Heat Capacity
Specific Heat Capacity :
The energy supplied by heating process to increase the temperature of an object with a mass of 1 kg by 1 K (or C)
Energy needed (released)
= Mass  Specific Heat Capacity  the temperature raised (lowered) in °C

10. Heat and Internal Energy 7
Temperature
Heat and Internal Energy 7
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Specific heat capacities of common materials
Substance
Specific heat capacity (J kg-1°C-1)
Water
4200
Methylated spirit
2400
Ice
2100
Aluminium
900
Glass
670
Iron
460
Lead
130

11. Heat and Internal Energy 8
Temperature
Heat and Internal Energy 8
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Worked Examples
Example 1
Calculation
Example 2
Calculation
Applications
Explanation

12. END of Temperature

13. Temperature 1 Temperature Next Slide
Temperature scale : we choose two temperatures called the fixed points. We define the scale of temperature according to these two fixed points.
Celsius scale : lower fixed point (ice point) and upper fixed point (steam point)
Lower fixed point : temperature of melting point under normal atmospheric pressure is taken as 0C
Upper fixed point : temperature of steam over boiling water at normal atmospheric pressure is taken as 100C

14. Temperature 1 Temperature Next Slide melting ice 0C lower fixed point
boiling water
100C
upper fixed point
Two marks are made on the thermometer to indicate the positions of lower fixed point (0C) and upper fixed point (100C).

15. Back to Temperature 1 Temperature Click Back to
Celsius temperature scale:
0C
10C
20C
30C
40C
50C
60C
70C
80C
90C
100C
Kelvin temperature scale :
Kelvin temperature = Celsius temperature + 273
e.g. 0C = 273 K, 100C = 373 K, 273C = 0 K
0C
10C
20C
30C
40C
50C
60C
70C
80C
90C
100C
273K
283K
293K
303K
313K
323K
333K
343K
353K
363K
373K

16. Back to Temperature 2 Temperature Click Back to
Mercury-in-glass thermometer :
It is a narrow glass tube. One end of the tube is made into a bulb which contains mercury and the other end is sealed.
Normal temperature range measured : 10C - 100C
Maximum temperature range measured : 39C - 357C

17. Back to Temperature 2 Temperature Click Back to
Alcohol-in-glass thermometer:
It is a narrow glass tube. One end of the tube is made into a bulb which contains alcohol while the other end is sealed.
Normal temperature range measured : 30C - 60C
Maximum temperature range measured : 115C - 78C

18. Back to Temperature 2 Temperature Click Back to
Clinical thermometer is shown below :
It is a special mercury-in-glass thermometer with a narrow bend in the tube. The scale used contains only a few degrees above and below the normal body temperature of 37C. It is used to measure the body temperature.

19. Back to Temperature 3 Temperature Click Back to Rotary thermometer: 2020 40 60 80
When the bimetallic strip with the pointer is heated, it bends because the metal on one side expands more than the metal on the other side.

20. Heat and Internal Energy 1
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Structure of a solid:
particles vibrate and have K.E.
P.E. depends on the relative
position of the particles

21. Heat and Internal Energy 2
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A solid is hammered as shown below :
The particles are then forced to vibrate more vigorously, hence they possess more K.E. Temperature, which is a measure of the average K.E. of the particles, rises.

22. Heat and Internal Energy 2
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A solid is in contact with another solid with a higher temperature
The particles in the solid with a lower temperature are forced to vibrate more vigorously (temperature rises). On the other hand, the particles in the solid with a higher temperature vibrate less vigorously (temperature drops).

23. Heat and Internal Energy 4
Temperature
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Kilowatt-hour meter:

24. Heat and Internal Energy 4
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Joulemeter :

25. Heat and Internal Energy 4
Temperature
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The following set-up is used to investigate the relation between the energy supplied and the rise in temperature.
to power
supply
polystyrene
cup
stirrer
water
thermometer
immersion
heater
Joulemeter or kilowatt-hour meter

26. Heat and Internal Energy 4
Temperature
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Results obtained : 50
100
150
200
250
300 20 23 26
28.5 32 35 37 3 6
8.5 12 15 17
Energy transfer E (J)
Temperature T (C)
Temperature rise T (C)
Energy transfer E
temperature rise T (C)
graph of E vs. T

27. Heat and Internal Energy 4
Temperature
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We obtain a straight line which passes through the origin. This means that for a constant mass, the energy transfer is directly proportional to the temperature rise, that is, E  T for constant m.
Then we investigate how the energy transfer is related to the mass of water. The time taken to heat different masses of water through the same temperature rise, say 10C.
Results obtained :
135
172
221
248
0.15
0.20
0.25
0.30
Energy transfer E (J)
Mass of water m (kg)

28. Heat and Internal Energy 4
Temperature
Heat and Internal Energy 4
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Energy transfer E
mass of water m (kg)
graph of E vs. m
Again, we obtain a straight line which passes through the origin. This means that for a given temperature change, the energy transfer is directly proportional to the mass of water, that is, E  m for constant T.

29. Heat and Internal Energy 4
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Temperature
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The polystyrene cup is used to hold the water. It is a bad conductor and so the energy lost to the surroundings is reduced. Moreover, it takes up little energy.
The stirrer is used to stir the water to maintain a homogeneous temperature in the water.
The Joulemeter (or kilowatt-hour meter) can measure the energy supplied to the immersion heater. The unit of the heater is kWh (kilowatt-hour). 1 kWh = J

30. Heat and Internal Energy 8
Temperature
Heat and Internal Energy 8
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2.25 kg of oil is put into the following set-up.
polystyrene
cup
stirrer
oil
thermometer
immersion
heater
Initial reading of Joulemeter : J
Final reading of Joulemeter : J
Initial temperature : 30C
Initial temperature : 70C

31. Heat and Internal Energy 8
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Temperature
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Energy supplied by the Joulemeter = (82500  42500) J = J
Rise in temperature = (70  30)C = 40C
Heat capacity of the oil =
Specific heat capacity of the oil =

32. Heat and Internal Energy 8
Temperature
Heat and Internal Energy 8
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2 kg of hot water at 80C is mixed with 4 kg of cold water at 20C. Suppose no energy is lost to the surroundings, what is the final temperature of the water? (Specific heat capacity of water : J kg-1 C -1.

33. Heat and Internal Energy 8
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Let T°C be the final temperature
Energy lost by the 2 kg water :
Energy gained by the 4 kg water :
By the principle of conservation of energy,
the amount of energy lost by the hot body
= the amount of energy gained by the cold body

34. Heat and Internal Energy 8
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Since water has a relatively high specific heat capacity, it needs a large amount of energy to raise the temperature of water.
Coolant of the engine of motor cars
Regulate the temperature of living organisms
Regulate the temperature of the land near the sea