Physics of Heat Transfer

Physics Module Form 4 Chapter 4 - Heat GCKL 2010

4.1
4 UNDERSTANDING THERMAL EQUILIBRIUM

What is
thermal
equilibrium ?

1. (______, Temperature ) is a form of energy that flows from a hot body to a cold
body.
2. The SI unit for (______, temperature) is Joule, J.
3. ( Heat , _____________ ) is the degree of hotness of a body
4. The SI unit for (heat , ___________) is Kelvin, K.
5. When thermal equilibrium is reached, the net rate of heat flow between the two
bodies is (______, equal)
6. There is no net flow of heat between two objects that are in thermal equilibrium.
Two objects in thermal equilibrium have the …______ … temperature
irrespective of shape, mass, size or type of surface.

Calibration of
thermometer

7. The ______ ______ of an object is important in the construction of a
thermometer. It is a physical quantity which is sensitive to and changes linearly
with the change in temperature of the object.

4-1


8. ________________ (l 0 )/ ice point : the temperature of pure melting ice/00C
9. ________________ ( l 100)/steam point: the temperature of steam from water
that is boiling under standard atmospheric pressure /1000C
10. The lengths of the mercury column in the mercury-in-glass thermometer is 2.6 cm
at 0OC and 22.6 cm at 100OC. When the thermometer is placed in hot water, the
length of the mercury column is 16.9 cm. Calculate the temperature of the hot
water.

Answer :

Liquid-in-glass 11. The liquid used in glass thermometer should
thermometer (a) Be easily ______
(b) Expand and contract rapidly over a ______ range of temperature
(c) Not ______ to the glass wall of the capillary tube
12. List the characteristic of mercury
(a) ______ liquid
(b) Does not ______ to the glass
(c) ______ uniformly when heated
(d) ______ point -390C
(e) ______ point 3570C
13. Which modification increases the sensitivity of the thermometer ?
A. Increasing the size of the bulb
B. Increasing the thickness of the bulb
C. Reducing the diameter of the capillary tube
D. Reducing the length of the capillary tube

4-2


Check Yourself 1

1. The diagram below shows a thermometer is
used to measure the temperature of hot water.
When the thermometer and the hot water are in
thermal equilibrium, which of the following is
not correct ?

4. Diagram below shows the liquid levels from
the bulb in three thermometers P, Q and R at
certain temperatures.
A. The temperature of hot water is equal to the
temperature of the thermometer
B. No heat flow between thermometer and hot
water
C. Heat flows from hot water to thermometer
D. Heat flows from thermometer to hot water

2. Which of the following characteristics does a
liquid-in-glass thermometer work ?
What is the temperature reading at
A. Volume of a fixed mass of liquid
thermometer R ?
B. Length of the liquid
C. Resistance of the liquid
A. 70.8 OC
D. Pressure of the liquid
B. 65.4 OC
C. 62.5 OC
D. 57.7 OC

3. Which of the following temperatures
corresponds to zero on the Kelvin scale ?

A. 273 OC
B. 0 OC
C. -273 OC
D. 100 OC

4-3


4.2
4 UNDERSTANDING SPECIFIC HEAT CAPACITY

Definition of Heat Capacity 1. Quantity of ______ energy required to raise the temperature of an object by
10C.

2. The unit of heat capacity is ______

3. Beaker A has (greater, same, less) heat capacity than beaker B.

B
A
A
A

4. This means that the (bigger, smaller) the mass, the (larger, smaller) the
amount of heat stored.

Definition of Specific Heat 1. Quantity of ______ energy required to raise the temperature of ______of a
Capacity substance by 10C.

2. The unit of specific heat capacity is ______

3. An object with low specific heat capacity can be heated up______, as it
requires less heat to increase its temperature by 10C. It can be cooled
______due to little amount of heat stored in it.

4. An object with high specific heat capacity takes ______ time to heat up, as it
requires more heat to increase its temperature by 10C. It is ______ to cool
down due to larger amount of heat stored in it.

Q = Pt
Pt = mc
Q = Heat supplied
P = Power of heater
T = Time in seconds
M = mass of substance
C = Specific heat capacity
 = Increase in
temperature

4-4


Determining the heat capacity
of aluminium block
1. The purpose of wrapping the aluminium blok with wool ______ ______to or
______ of heat from the surrounding.

2. Oil in the holes for housing thermometer and the immersion heater is to
improve the ______ of heat from the heater to the thermometer through the
aluminium block.

3. The immersion heater of 50 W rated power is used for 5 minutes to heat up
the aluminium block. If the mass of the alumimium block is 1.0 kg and the
rise in temperature is 160C, what is the specific heat capacity of aluminium ?

Pt 15000
C   937.5 Jkg-10C-1
m 1 16

4. Specific heat capacity calculated is usually ______ than the standard value
because some ______is lost to the surroundings.

Aim To investigate the relationship between temperature rise and mass of water

Experiment

800C 600C 800C 400C

Hypothesis When the mass of water …______ … the temperature rise will …______ ….

Manipulated variable ______ of water

Responding variable ______ in temperature

Fixed variable ______ duration, water, weighing scale, ______ rating of heater used

Apparatus Thermometer, water, beaker water, weighing scale

Setup

4-5


Procedure

1. 100 ml of water is placed in a 500 ml beaker.

2. A heater is placed in the water.

3. Heating process is carried out for 1minute.

4. Highest temperature achieved is recorded.

5. Step 2 to 4 is repeated for 200ml, 300ml, 400ml and 500ml of water.

Analysis
Volume of Final Initial Rise in 1/ (0C-1)
water used, temperature, temperature, temperature,
V (ml) T2 (0C) T1 (0C)  = T2 – T1
(0C)

100

200

300

400

500

V
Conclusion

1/

Applications of specific heat capacity

Water as heating agent in
heating radiator

4-6


2. Heat from hot water is
released to the cooler
surroundings of a room to
achieve _____ _____
3. Cold water will be
recirculated to repeat
the process continously

1. Cool water is pumped into the hot
water reservoir to absorb a large amount
of heat due to its ______specific heat
capacity.

4. Hot water is
cooled by the
air from the
Water as a coolant in car cooling fins
and the fan 2. ______ specific heat
engine
capacity of water allows it
to absorb a large amount
of ______from the
engine

3. Cool water is recirculated
through the engine blocks 1. Cool water is pumped
and the process continues into the hot engine
while the engine is running

3. Cool air
2. Hot air rises up blows from
from the land the sea to
replace the
space left by
1. During the day the hot air
Sea Breeze land gets hotter and
than the sea ______
because c land c sea currents in
(wind from the sea)
the air are
formed

3. Cooler
air blows
from the 2. hot air rises
land to from the sea
replace the
space left
Land Breeze (wind from the by the hot
1. During the
land) air and
night, the sea
convection
is hotter than
currents in
the land
the air are
because
formed.
c land c sea

4-7


Plastic handle _____specific heat capacity

Household apparatus and
utensils
Steel ______specific heat
capacity

3. Diagram below shows a bullet moving at a
velocity of 60 ms-1 is embedded in a wooden
Check Yourself 1 block.
1. Table below shows four types of liquid with
their respective specific heat capacities and
boiling points. All the liquids have the same
mass and same temperatures of 30oC. If the
same amount of heat is supplied to them,
which liquid, A, B, C or D will boil first ? Assuming all the energy lost by the bullet is
Liquid Specific heat Boiling point converted to heat energy and is absorbed by
capacity (Jkg-10C-1) (oC) the bullet. What is the rise in temperature of
the bullet ? ( Specific heat capacity of the
A 3.0 50 bullet = 120 Jkg-10C-1)
B 5.0 80 A. 0.5 oC

C 4.2 100 B. 2.0 oC
C. 30.0 oC
D 0.2 200
D. 60.0 oC
2. Table below shows the specific heat capacity
4. Diagram below shows 200 g of water at 0 oC is
of four different metals.
poured into a cup containing 400 g of water at
80 oC . Assuming there is no heat loss to the
surroundings.

Which of the following is the most suitable
metal to be used in a rice cooker for fast What is the final temperature of the mixture ?
heating ? [ Specific heat capacity of water = 4200 Jkg-10C-1]

A. P A. 53 oC
B. Q
B. 60 oC
C. R
C. 66 oC
D. S
D. 70 oC

4-8


5. Diagram below shows the temperature-time
graph of two solids X and Y of equal mass but
of different substances are heated
simultaneously by identical heaters.

Which of the following comparison is correct?

A. Cx > Cy

B. Cx < Cy

C. Cx = Cy

4-9


4.3
4 UNDERSTANDING SPECIFIC LATENT HEAT

Definition of 1. Latent Heat is the total energy ________ or released when a substance changes
Latent Heat its ________ state completely at a ________ temperature.

2. Latent Heat of fusion is heat absorbed when ________ changes into ________ or
heat released when liquid changes into solid at constant________.

3. Latent Heat of vaporization is heat absorbed when ________ changes into
________or heat released when vapour changes into liquid at constant________.

4. Unit for latent heat is ________ .

5. Process in which solid directly changes into vapour is called ________ .

1. Specific Latent Heat of fusion is heat absorbed when 1 kg ________changes into
________or heat released when liquid changes into solid at constant________ .
Definition of
Specific Latent 2. Specific Latent Heat of vaporization is heat absorbed when 1 kg ________
Heat changes into ________or heat released when vapour changes into liquid at
constant________ .

3. Unit for latent heat is________.

4. When temperature remain constant, ________energy of the molecules remain
constant. However energy absorbed is used to overcome ________ of attraction
and atmospheric pressure.

4-10


Heating curve Fill the empty boxes for the heating curve below with the following words

Solid, liquid, gas, boiling point, melting point,
latent heat of fusion, latent heat of vaporization

Calculation of
specific latent
heat of fusion

Mass of water collected in Set A = 49.2 g
Mass of water collected in Set B = 6.4 g
Power of heater = 80 W
Time interval of switching on the heater = 3 minutes

1. Calculate energy supplied by the heater.

2. What is the mass of ice melted due to the heat absorbed from the
surroundings?

3. Determine the specific latent heat of fusion of ice.

Pt (80)(3  60) 14400
L= = = =
m (49.2  6.4) 10 3
42.8 103

4-11


Check Yourself 1

1. Diagram below shows the cooling curve of a power of 1 kW. The beaker and its content is
Gas. Temperatures T1 and T2 represents resting on an electronic balance which
measures the mass of the beaker and its
content.

T1 T2

A. Solidification Room temperature

B. Boiling Point Solidification point
When the water is boiling, it is found that 80 g
C. Melting Point Freezing Point of water is boiled away in 3 minutes.

D. Melting Point Room temperature What is the specific latent heat of vaporization
of water ?
2. Diagram below shows the heating curve of a
solid Y of mass 2 kg which is heated by a A. 2.10 x 106 Jkg-1
heater of 70 W power. Which statement B. 2.15 x 106 Jkg-1
below is NOT true ?
C. 2.20 x 106 Jkg-1

D. 2.25 x 106 Jkg-1

4. Diagram below shows the arrangement of
apparatus used to determine the specific latent
heat of fusion of ice. There are two identical
sets. One of the sets is called a control set
which is without a power supply.

A. Specific latent heat of Y is 10500 Jkg-1.

B. Specific heat capacity of solid Y and
liquid Y are the same

C. Total heat used is 1120 J

D. Melting point of Y is 10 oC The aim of the control set is

3. Diagram below shows the arrangement of
apparatus used to determine the specific latent
heat of vaporization of water. The water in the
beaker is heated by an immersion heater with a
4-12


A. To find the mass of ice melted due to the C. To detect any changes in the melting point
heat absorbed from the surroundings of the ice

B. To find the mass of water formed by D. To find the mass of water evaporated
condensation from the vapour in the air

5.

Heat produced in an engine block of car needs to be transferred out promptly to prevent overheating. This is
done by circulating a suitable cooling liquid through the engine block.
(a) What is meant by ‘specific heat capacity of water is 4200 Jkg-1oC-1 ?

________________________________________________________________________________
(b) Based on the table above,
(i) Explain the suitable characteristics of the cooling liquid to extract heat out of an engine block.
High Specific Heat Capacity
High specific latent heat of
vaporization
High boiling point
Low rusting rate

(ii) Decide which liquid is the most suitable and give reasons for your choice.

_____________________________________________________________________________
(c) Total energy released by an engine in 1 hour = 9.0 x 107 J
Energy breakdown : mechanical 40% and heat 60%
Mass of cooling liquid circulating in 1 hour = 150 kg
Temperature of water entering the engine = 30oC
Temperature of water exiting the engine = 60oC
Based on the information above,
(i) Calculate the power of the engine

(ii) Calculate the amount of heat produced by the engine in one hour.

(iii) Calculate the specific heat capacity of the cooling liquid.

4-13


(d) Suggest two ways to dissipate the heat from the cooling liquid.

1. ______________________________________________________________________________

2. ______________________________________________________________________________

4-14


4.4
4 UNDERSTANDING GAS LAWS

What is The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules),
kinetic theory all of which are in constant, _______ _______. The rapidly moving particles constantly collide with
of gases ? each other and with the walls of the container. Kinetic theory explains ___________ properties of
gases, such as pressure, temperature, or volume, by considering their molecular composition and
motion.

The ___________ of an ideal __________ ____ is a measure of the average _______ _______ of its
atoms.

Boyles’ Law Charles’ Law Pressure Law

Define the Formula
three gas
laws.

Condition T = ___________and P = ______ and V = ______ and
_______ of gas are _____ of gas are constant ____ of gas are constant
constant (temperature must be in (temperature must be in
______scale) ______ scale)

Graphs

4-15


Experiment
al set up

Calculation Diagram on the right shows an arrangement to investigate the
involving relationship between pressure and volume of a fixed mass of gas
Boyle’s Law.
at constant temperature. The pressure of the air in the glass tube is
measured by a pressure gauge and the pressure can be
increased by using the bicycle pump. The pump of the gas is 1.5
x 105 Pa when the volume is 80 cm3.

(a) Explain how a gas exerts a pressure on the walls of its container.
__________________________________________________________________________

__________________________________________________________________________

(b) State the Boyle’s law.
__________________________________________________________________________

__________________________________________________________________________

(c) Find the volume of the gas when pressure is 2.5 x 105 Pa

(d) Find the pressure of the gas when the volume of the gas is 60 cm3.

(e) A bubble of air rises from the bottom of a pond to the surface. As the bubble reaches the
surface, its volume is double its original volume. Assume the temperature is constant, find
the depth of the pond. [Atmospheric pressure = 10 m of water]

4-16


Question (a) State Charles’ law.
involving __________________________________________________________________________
Charles’
__________________________________________________________________________
Law.
(b) Diagrams below shows how (a) the pressure of the gas change with temperature and (b) the
volume of the gas change with temperature .

(a) (b)

(i) Compare the characteristics displayed by the graphs.

1. _______________________________________________________________
2. _______________________________________________________________
3. _______________________________________________________________
(ii) Relate the information you have mentioned to form a physics concept.

______________________________________________________________________

______________________________________________________________________
(iii) Name the concept.

______________________________________________________________________

(c) (i) Define pressure.

______________________________________________________________________

(iv) Using kinetic theory of gas, explain why the pressure of a gas in a fixed container
increases with an increase in its temperature.

1. _______________________________________________________________
2. _______________________________________________________________
3. _______________________________________________________________

4-17


Questions Diagram (a) shows the conditon of a snack pack kept in a refrigerator at 18oC, whereas Diagram (b)
involving shows the condition of the same snack pack in Borneo Highlands at the same temperature at 18oC.
Pressure Law.

(a) (b)

Based on the above information and observation,

(a) State one suitable inference.
______________________________________________________________________

(b) State one suitable hypothesis.
______________________________________________________________________

(c) With the use of appropriate apparatus, describe an experiment framework to test your
hypothesis. In your description, state clearly the following:

(i) Aim of the experiment

______________________________________________________________________

(ii) Variables used in the experiment

_______________________________________________________________
_______________________________________________________________
_______________________________________________________________

(iii) List of apparatus and materials

_________ pressure gauge, a _______ with volume scale, rubber tube and retort
stand.

(iv) Arrangement of the apparatus

4-18


(v) The procedure of the experiment which include the method of controlling the
manipulated variable and the method of measuring the responding variable

1. The apparatus for the experiment is set up as shown in the diagram
2. The ______ of the syringe is pressed down slowly until the volume of air inside
the syringe is 100 cm3
3. The ________ of the air in the syringe is read from the Bourdon gauge
4. The experiment is repeated with ________of air fixed at 80 cm3,
5. Make sure that there is no _____ and no increase in ___________ .
6.
(vi) The way you would tabulate the data
Volume, V (cm3) Pressure, P (Pa)

100.0
(vii) The way you would analyze the data
80.0

60.0

40.0

20.0

Check Yourself 1

1. Diagram below shows a valve P connecting A. 2.0 x 10 -4 m3
two cylinders, A dan B. When P is opened,
gas from cylinder A moves to cylinder B. B. 4.0 x 10 -4 m3

C. 5.0 x 10 -4 m3
P
D. 8.0 x 10 -4 m3

3. Diagram below shows capillary tubes (a) and
Which physical quantities does not change ? (b) which are identical. If the atmospheric
pressure is 75 cmHg, determine the length of
A. Pressure gas column x and the pressure p.
B. Volume
C. Mass
D. Density

2. The graph in the diagram
below shows the
relationship between
pressure, P and volume, V
of a fixed mass of gas at
constant temperature. Length Pressure
What is the value of V2 ? x (cm) p (cmHg)

4-19


A. 24.0 70
B. 21.0 75
C. 22.4 80 5. Air at a temperature of 27oC is kept in a
D. 21.0 70 container at a pressure of 1 atmosphere. What
is the pressure of the air, in atmosphere, if it is
4. Diagram below shows a fan is allowed to blow heated to a temperature of 77oC ?
in a closed room for an hour. What are the A. 0.35
possible changes to the pressure and B. 0.86
temperature of the air in the room ? C. 1.17
D. 2.85

6. Table below shows the volume and
temperature of a fixed mass of gas kept at
constant pressure.

V (cm3) 50 100
T(oC) 27 x

Temperature Pressure
What is the value of x ?
A. Increases no change
B. No change increases A. 54 oC
C. Decreases increases B. 300 oC
D. Increases Increases C. 327 oC
D. 600 oC

4-20

Physics of Heat Transfer

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