Chapter 4 : Heat
Physics Module Form 4
Students CopyChapter 4: Heat
4.1 : UNDERSTANDING THERMAL EQUILIBRIUM
By the end of this subtopic, you will be able to
Explain thermal equilibrium
Explain how a liquid-in glass thermometer works
1. The net heat will flow from A to B until the temperature of A
is the ( same, zero as the temperature of B. In this situation, the
two bodies are said to have reached thermal equilibrium.
2. When thermal equilibrium is reached, the net rate of heat
flow between the two bodies is (zero, equal)
3. There is no net flow of heat between two objects that are in
thermal equilibrium. Two objects in thermal equilibrium have the
temperature.
4. The liquid used in glass thermometer should
(a) Be easily seen
(b) Expand and contract rapidly over a wide range of
temperature
(c) Not stick to the glass wall of the capillary tube
5. List the characteristic of mercury
(a) Opaque liquid
(b) Does not stick to the glass
(c) Expands uniformly when heated
(d) Freezing point -390C
(e) Boiling point 3570C
6. ( Heat, Temperature ) is a form of energy. It flows from a
hot body to a cold body.
7. The SI unit for ( heat , temperature) is Joule, J.
8. ( Heat , Temperature ) is the degree of hotness of a body
9. The SI unit for (heat , temperature) is Kelvin, K.
10. Lower fixed point (l 0 )/ ice point : the temperature of
pure melting ice/00C
11. Upper fixed point( l 100)/steam point: the temperature of
steam from water that is boiling under standard atmospheric
pressure /1000C
Exercise 4.1
Section A: Choose the best answer
1. The figure shows two metal blocks. Which the following
statement is false?
A. P and Q are in thermal contact
B. P and Q are in thermal equilibrium
C. Energy is transferred from P to Q
D. Energy is transferred from Q to P
2. When does the energy go when a cup of hot tea cools?
A. It warms the surroundings
B. It warms the water of the tea
C. It turns into heat energy and disappears.
3. Which of the following temperature corresponds to zero on the
Kelvin scale?
A. 2730 C
B. 00C
C. -2730 C
D. 1000 C
4. How can the sensitivity of a liquid- in glass thermometer be
increased?
A. Using a liquid which is a better conductor of heat
B. Using a capillary tube with a narrower bore.
C. Using a longer capillary tube
D. Using a thinner-walked bulb
5. Which instrument is most suitable for measuring a rapidly
changing temperature?
A. Alcohol-in glass thermometer
B. Thermocouple
C. Mercury-in-glass thermometer
D. Platinum resistance thermometer
6. When shaking hands with Anwar, Kent Hui niticed that Anwars
hand was cold. However, Anwar felt that Kent Hui hand was warm. Why
did Anwar and Kent Hui not feel the same sensation?
A. Both hands in contact are in thermal equilibrium.
B. Heat is flowing from Kent Huis hand to Anawrs hand
C. Heat is following from Anwars hand to Kent Hui hand.
Section B: Answer all the questions by showing the
calculation
1. The length of the mercury column at the ice point and steam
point are 5.0 cm and 40.0cm respectively. When the thermometer is
immersed in the liquid P, the length of the mercury column is 23.0
cm. What is the temperature of the liquid P?
2. The length of the mercury column at the steam point and ice
point and are 65.0 cm and 5.0cm respectively. When the thermometer
is immersed in the liquid Q, the length of the mercury column is
27.0 cm. What is the temperature of the liquid Q?
Temperature, = l l0 x 1000C
l100 l0
= 27 5 x 1000C
65 - 5
= 36.670C
3. The distance between 00C and 1000C is 28.0 cm. When the
thermometer is put into a beaker of water, the length of mercury
column is 24.5cm above the lower fixed point. What is the
temperature of the water?
4. The distance between 00C and 1000C is 25 cm. When the
thermometer is put into a beaker of water, the length of mercury
column is 16cm above the lower fixed point. What is the temperature
of the water? What is the length of mercury column from the bulb at
temperatures i) 300C
SECTION C: Structured Questions
1. Luqman uses an aluminium can, a drinking straw and some
plasticine to make a simple thermometer as shown in figure below.
He pours a liquid with linear expansion into the can.
(a) Suggest a kind of liquid that expands linearly. (1m)
.
(b) He chooses two fixed points of Celsius scale to calibrate
his thermometer. State them (2m)
(c) If the measurement length of the liquid inside the straw at
the temperature of the lower fixed point and the upper fixed point
are 5cm and 16 cm respectively, find the length of the liquid at
82.50C.
(d) Why should he use a drinking straw of small diameter?
(e) What kind of action should he take if he wants to increase
the sensitivity of his thermometer?
2. What do you mean by heat and temperature?
....
4.2 : UNDERSTANDING SPECIFIC HEAT CAPACITY
By the end of this subtopic, you will be able to
Define specific heat capacity
State that c = Q/MC
Determine the specific heat capacity of a liquid
Determine the specific heat capacity of a solid
Describe applications of specific heat capacity
Solve problems involving specific heat capacity
1. The .. of a body is the .. that must be supplied to the body
to increase its temperature by 10C.
2. The heat capacity of an object depends on the
(a) .
(b) .
(c)
3. The of a substance is the amount of heat that must be
supplied to increase the temperature by 1 0C for a mass of 1 kg of
the substance. Unit Jkg-1 K-1
4. The heat energy absorbed or given out by an object is given
by Q = mcO.
5. High specific heat capacity absorb a large amount of heat
with only a temperature increase such as plastics.
6. Conversion of energy
7. Applications of Specific Heat Capacity
Explain the meaning of above application of specific heat
capacity:
(a) Water as a coolant in a car engine
(i)
....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
(b) Household apparatus and utensils
...
...
...
...
(c) Sea breeze
(d) Land breeze
Exercise 4.2
SECTION A : Choose the best answer
1. The change in the temperature of an object does not depend
on
A. the mass of the object
B. the type of substance the object is made of
C. the shape of the object
D. the quantity of heat received
2. Which of the following defines the specific heat capacity of
a substance correctly?
A. The amount of heat energy required to raise the temperature
of 1kg of the substance
B. The amount of heat energy required to raise 1kg of the
substance by 10C.
C. The amount of heat energy required to change 1kg of the
substance from the solid state to the liquid state.
3. Heat energy is supplied at the same rate to 250g of water and
250g of ethanol. The temperature of the ethanol rises faster. This
is because the ethanol..
A. is denser than water
B. is less dense than water
C. has a larger specific heat capacity than water
D. has a smaller specific heat capacity than water
4. In the experiment to determine the specific heat capacity of
a metal block, some oil is poured into the hole containing
thermometer. Why is this done?
A. To ensure a better conduction of heat
B. To reduce the consumption of electrical energy
C. To ensure the thermometer is in an upright position.
D. To reduce the friction between the thermometer and the wall
of the block.
SECTION B: Answer all questions by showing the calculation
1. How much heat energy is required to raise the temperature of
a 4kg iron bar from 320C to 520C? (Specific heat capacity of iron =
452 Jkg-1 0C-1).
2. Calculate the amount of heat required to raise the
temperature of 0.8 kg of copper from 350C to 600C. (Specific heat
capacity of copper = 400 J kg-1 C-1).
3. Calculate the amount of heat required to raise the
temperature of 2.5 kg of water from 320C to 820C. (Specific heat
capacity of water = 4200 J kg-1 C-1).
4. 750g block of a aluminium at 1200C is cooled until 450C. Find
the amount of heat is released. . (Specific heat capacity of
aluminium = 900 J kg-1 C-1).
5. 0.2 kg of water at 700C is mixed with 0.6 kg of water at
300C. Assuming that no heat is lost, find the final temperature of
the mixture. (Specific heat capacity of water = 4200 J kg-1
C-1)
SECTION C: Structured questions
1. In figure below, block A of mass 5kg at temperature 1000C is
in contact with another block B of mass 2.25kg at temperature
200C.
Assume that there is no energy loss to the surroundings.
(a) Find the final temperature of A and B if they are in thermal
equilibrium. Given the specific heat capacity of A and B are 900
Jkg-1 C-1 and 400 Jkg-1 C-1 respectively.
(b) Find the energy given by A during the process.
(c) Suggest one method to reduce the energy loss to the
surroundings.
..
4.3 UNDERSTANDING SPECIFIC LATENT HEAT
By the of this subtopic, you will be able to
State that transfer of heat during a change of phase does not
cause a change in temperature
Define specific latent heat
State that l = Q/m
Determine the specific latent heat of fusion and specific latent
heat of vaporisation
Solve problem involving specific latent heat.
1. Four main changes of phase.
2. The heat absorbed or the heat released at constant
temperature during a change of
phase is known as latent heat. Q= ml
3. Complete the diagrams below and summarized.
(a) Melting
(b) Boiling
(c) Solidification
(d) Condensation
4. is the heat absorbed by a melting solid. The specific latent
heat of fusion is the quantity of the heat needed to change 1kg of
solid to a liquid at its melting point without any increase in ..
The S.I unit of the specific latent heat of fusion is Jkg-1.
5. ... is heat of vaporisation is heat absorbed during boiling.
The specific latent heat of vaporisation is the quantity of heat
needed to change 1kg of liquid into gas or vapour of its boiling
point without any change in .. The S.I unit is Jkg-1.
6. Explain the application of Specific Latent Heat above:
:
(d) Cooling of beverage
(e) Preservation of Food
(f) Steaming Food
(g) Killing of Germs and Bacteria
EXERCISE 4.3
Section A:
1. The graph in figure below shows how the temperature of some
wax changes as it cools from liquid to solid. Which section of the
graph would the wax be a mixture of solid and liquid?
A. PQ
B. QR
C. RS
D. ST
2. Figure show a joulemeter used for measuring the electrical
energy to melt some ice in an experiment. To find the specific
latent heat of fusion of ice, what must be measured?
A. The time taken for the ice to melt
B. The voltage of the electricity supply
C. The mass of water produced by melting ice
D. The temperature change of the ice.
3. It is possible to cook food much faster with a pressure
cooker as shown above. Why is it easier to cook food using a
pressure cooker?
A. More heat energy can be supplied to the pressure cooker
B. Heat loss from the pressure cooker can be reduced.
C. Boiling point of water in the pressure cooker is raised
D. Food absorbs more heat energy from the high pressure
steam
4. Which of the following is not a characteristics of water that
makes it widely used as a cooling agent?
A. Water is readily available
B. Water does not react with many other substance
C. Water has a large specific heat capacity
D. Water has a large density
5. Figure below shows the experiment set up to determine the
specific latent heat of fusion of ice. A control of the experiment
is set up as shown in Figure (a) with the aim of
A. determining the rate of melting of ice
B. ensuring that the ice does not melt too fast.
C. determining the average value of the specific latent heat of
fusion of ice.
D. determining the mass of ice that melts as a result of heat
from the surroundings
6. Scalding of the skin by boiling water is less serious then by
steam. This is because
A. the boiling point of water is less than the temperature of
steam
B. the heat of boiling water is quickly lost to the
surroundings
C. steam has a high specific latent heat.
D. Steam has a high specific heat capacity.
SECTION B: Answer the question by showing the calculation
1. 300g of ice at 00C melts. How much energy is required for
this
Question 2-7 are based on the following information
Specific heat capacity of water = 4 200 J kg-1 C-1
Specific heat capacity of ice = 2 100 J kg-1 C-1
Specific latent heat of fusion of ice = 3.34 X 105J kg-1
Specific latent heat of vaporization of water = 2.26 X 106 J
kg-1
2. An immersion heater rated at 500 W is fitted into a large
block of ice at 00C. How long does it take to melt 1.5kg of
ice?
3. 300 g of water at 400C is mixed with x g of water at 800C.
The final temperature of the mixture is 700C. Find the value of
x
4. Calculate the amount of heat released when 2 kg of ice at 00C
is changed into water at 00C.
5. Calculate the amount of heat needed to convert 3 kg of ice at
00C to water at 300C.
6. Find the amount of heat needed to convert 0.5 kg of ice at
150C into steam at 1000C
7. Calculate the amount of heat needed to convert 100 g of ice
at 00C into steam at 1000C.
8. The specific latent heat of vaporization of water is 2300 kJ
kg-1. How much heat will be absorbed when 3.2 kg of water is boiled
off at its boiling point.
4.4 UNDERSTANDING THE GAS LAW
By the end of this subtopic; you will be able to :
Explain gas pressure, temperature and volume in terms of the
behaviour of gas molecules.
Determine the relationship between
(i) pressure and volume
(ii) volume and temperature
(iii) pressure and temperature
Explain absolute zero and the absolute/Kelvin scale of
temperature
Solve problems involving pressure, temperature and volume of a
fixed mass of gas
1. Complete the table below.
Property of gas
Explanation
Volume,V
m3
Temperature,T
K (Kelvin)
Pressure,P
Pa(Pascal)
2. The kinetic theory of gas is based on the following
assumptions:
................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
4.4.1 Boyles Law
1. Boyles law states that...
............................................................................
2. Boyles law can be shown graphically as in Figure above
3. The volume of an air bubble at the base of a sea of 50 m deep
is 250cm3. If the atmospheric pressure is 10m of water, find the
volume of the air bubble when it reaches the surface of the
sea.
4.4.2 Charless Law
1. Charles law states .
The temperature -2730C is the lowest possible temperature and is
known as the absolute zero of temperature.
2. Fill the table below.
Temperature
Celsius scale (0C)
Kelvin Scale(K)
Absolute zero
Ice point
Steam point
Unknown point
3. Complete the diagram below.
4.4.3 Pressures Law
1. The pressure law states ....
..
EXERSICE 4.4:Gas Law
1. A mixture of air and petrol vapour is injected into the
cylinder of a car engine when the cylinder volume is 100 cm3. Its
pressure is then 1.0 atm. The valve closes and the mixture is
compressed to 20 cm3. Find the pressure now.
2. The volume of an air bubble at the base of a sea of 50 in
deep is 200 cm3. If the atmospheric pressure is 10 in of water,
find the volume of the air bubble when it reaches the surface of
the sea.
3. The volume of an air bubble is 5 mm3 when it is at a depth of
h in below the water surface. Given that its volume is 15 mm3 when
it is at a depth of 2 in, find the value of h. (Atmospheric
pressure = 10 m of water)
4. An air bubble has a volume of V cm3 when it is released at a
depth of 45m from the water surface. Find its volume (V) when it
reaches the water surface. (Atmospheric pressure = 10 m of
water)
5. A gas of volume 20m3 at 370C is heated until its temperature
becomes 870C at constant pressure. What is the increase in
volume?
6. The air pressure in a container at 330C is 1.4 X 1O5 N m2.
The container is heated until the temperature is 550C. What is the
final air pressure if the volume of the container is fixed?
7. The volume of a gas is 1 cm3 at 150C. The gas is heated at
fixed pressure until the volume becomes triple the initial volume.
Calculate the final temperature of the gas.
8. An enclosed container contains a fixed mass of gas at 250C
and at the atmospheric pressure. The container is heated and
temperature of the gas increases to 980C. Find the new pressure of
the gas if the volume of the container is constant.(Atmospheric
pressure = 1.0 X 105N rn2)
9. The pressure of a gas decreases from 1.2 x 105 Pa to 9 x 105
Pa at 400C. If the volume of the gas is constant, find the initial
temperature of the gas.
PART A: CHAPTER 4
1. A 5kg iron sphere of temperature 500C is put in contact with
a 1kg copper sphere of temperature 273K and they are put inside an
insulated box. Which of the following statements is correct when
they reach thermal equilibrium?
D. A iron sphere will have a temperature of 273K
E. The copper sphere will have a temperature of 500C.
F. Both the sphere have the same temperature.
G. The temperature of the iron sphere will be lower than
500C
2. In the process to transfer heat from one object to another
object, which of the following processes does not involve a
transfer to material?
A. Convection
B. Vaporisation
C. Radiation
D. Evaporation
3. When we use a microwave oven to heat up some food in a lunch
box, we should open the lid slightly. Which of the following
explanations is correct?
A. To allow microwave to go inside the lunch box
B. To allow the water vapors to go out, otherwise the box will
explode
C. To allow microwave to reflect more times inside the lunch
box
D. To allow microwave to penetrate deeper into the lunch
box.
4. Water is generally used to put out fire. Which of the
following explanation is not correct?
A. Water has a high specific heat capacity
B. Steam can cut off the supply of oxygen
C. Water is easily available
D. Water can react with some material
5. Given that the heat capacity of a certain sample is 5000
J0C-1. Which of the following is correct?
A. The mass of this sample is 1kg.
B. The energy needed to increase the temperature of 1 kg of this
sample is 5000 J.
C. The energy needed to increase the temperature of 0.5kg of
this sample is 2500J.
D. The temperature of this sample will increase 10C when 5 000 J
energy is absorbed by this sample.
6. Which of the following statement is correct?
A. The total mass of the object is kept constant when fusion
occurs.
B. The internal energy of the object is increased when
condensation occurs
C. Energy is absorbed when condensation occurs.
D. Energy is absorbed when vaporization occurs.
7. Water molecules change their states between the liquid and
gaseous states
A. only when water vapour is saturated
B. at all times because evaporation and condensation occur any
time
C. only when the vapour molecules produce a pressure as the same
as the atmospheric pressure
D. only when the water is boiling
8. Based on the kinetic theory of gas which one of the following
does not explain the behaviour of gas molecules in a container?
A. Gas molecules move randomly
B. Gas molecules collide elastically with the walls of the
container
C. Gas molecules move faster as temperature increases
D. Gas molecules collide inelastically with each other
9. A cylinder which contains gas is compressed at constant
temperature of the gas increase because
A. the average speed of gas molecules increases
B. the number of gas molecules increases
C. the average distance between the gas molecules increases
D. the rate of collision between the gas molecules and the walls
increases
10. A plastic bag is filled with air. It is immersed in the
boiling water as shown in diagram below.
Which of the following statements is false?
A. The volume of the plastic bag increases.
B. The pressure of air molecules increases
C. The air molecules in the bag move faster
D. The repulsive force of boiling water slows down the movement
of air molecule
PART B;
1. A research student wishes to carry out an investigation on
the temperature change of the substance in the temperature range
-500C to 500C. The instrument used to measure the temperature is a
liquid in glass thermometer.
Thermometer
A
B
C
D
Liquid
Mercury
Mercury
Alcohol
Alcohol
Freezing point of liquid (0C)
-39
-39
-112
-112
Boiling point of liquid (0C)
360
360
360
360
Diameter of capillary tube
Large
Small
Large
Small
Cross section
Table 1
(a) (i) State the principle used in a liquid- in glass
thermometer.(1m)
........................................................................................................................................
(ii) Briefly explain the principle stated in (a)(i) (3m)
.
.
.
(b) Table 1 shows the characteristic of 4 types of thermometer:
A,B C and D. On the basis of the information given in Table 1,
explain the characteristics of, and suggest a suitable thermometer
for the experiment.(5 m)
..
(c) The length of the mercury column in uncalibrated thermometer
is 6.0cm and 18.5 cm at 00C and 1000C. respectively. When the
thermometer is placed in a liquid, the length of the mercury column
is 14.0cm
(i) Calculate the temperature of the liquid
(ii) State two thermometric properties which can be used to
calibrate a thermometer. (6m)
2. A metal block P of mass 500 g is heated is boiling water at a
temperature of 1000C. Block P is then transferred into the water at
a temperature of 300C in a polystyrene cup. The mass of water in
the polystyrene cup is 250 g. After 2 minutes, the water
temperature rises to 420C.
Assuming that the heat absorbed by the polystyrene cup and heat
loss to the surroundings are negligible.{Specific heat capacity of
water 4 200 j kg-1 C-1)
Calculate
(a) the quantity of heat gained by water the polystyrene cup
(b) the rate of heat supplied to the water
(c) the specific heat capacity of the metal block P
3. A student performs an experiment to investigate the energy
change in a system. He prepares a cardboard tube 50.0 cm long
closed by a stopper at one end. Lead shot of mass 500 g is placed
in the tube and the other end of the tube is also closed by a
stopper. The height of the lead shot in the tube is 5.0 cm as shown
in Figure 3.1. The student then holds both ends of the tube and
inverts it 100 times (Figure 3.2).
(a) State the energy change each time the tube is inverted.
..
..
(b) What is the average distance taken by the lead shot each
time the tube is inverted?
(c) Calculate the time taken by the lead shot to fall from the
top to the bottom of the tube.
(d) After inverting the tube 100 times, the temperature of the
lead shot is found to have increased by 30C.
i. Calculate the work done on the lead shot.
ii. Calculate the specific heat capacity of lead.
iii. State the assumption used in your calculation in (d)ii.
...
.
PART C: EXPERIMENT
1. Before travelling on a long journey, Luqman measured the air
pressure the tyre of his car as shown in Figure (a) He found that
the air pressure of the tyre was 200 kPa. After the journey, Luqman
measured again the air pressure of the tyre as shown in Figure (b)
He found that the air pressure had increase to 245 kPa. Luqman also
found that the tyre was hotter after the journey although the size
of the tyre did not change.
Using the information provided by Luqman and his observations on
air pressure in the tyre of his car:
Choose suitable apparatus such as pressure gauge, a
round-bottomed flask and any other apparatus that may he necessary.
In your description, state clearly the following:
i. Aim of the experiment,
ii. Variables in the experiment,
iii. List of apparatus and materials,
iv. Arrangement of the apparatus,
v. The procedure of the experiment including the method of
controlling the manipulated variable and the method of measuring
the responding variable,
vi. The way you would tabulate the data,
vii. The way you would analyse the data. [10 marks]
CHAPTER 4: HEAT
Thermal equilibrium :Keseimbangan terma
.. rate of energy transfer
Hot
object
Cold
object
.. rate of energy transfer
Equivalent to
Equivalent to
No net heat transfer
A
B
..
.
..
..
.
.
.
.
.
..
l0: length of mercury at ice point
l100: length of mercury at steam point
l: length of mercury at point
Temperature, =
l - l0
l100 - l0
x 1000C
Heat capacity
Muatan haba
Specific heat capacity
Muatan haba tentu
Specific heat capacity , c =
Q__
m
Electrical energy
Heat energy
Pt = mc
Heater
Power = P
energy
..energy
..energy
Object falls from
A high position
Moving object stopped due to friction
Power = P
Heat energy
mgh= mc
Heat energy
mv2= mc
Small value of c
Big value of c
Two object of equal mass
Equal rate of heat supplied
. increase in temperature
. increase in temperature
A
B
1000C
200C
5kg
2.25kg
Solid
Solidification
Latent heat
Boiling
Latent heat .
Condensation
Latent heat
Liquid
Gas
Temperature
Time
.
Temperature
Time
.
Temperature
Time
.
Temperature
Time
.
water
ice
water
gas
Small volume molecules hit wall more often, greater pressure
P 1
V
That is PV = constant
Or P1V1 = P2V2
Relationship between pressure and volume
0
P
1/V
(b) P directly proportional to 1/V
0
P
V
(a) P inversely proportional to V
PI=50m + 10m
V1=250cm3
P2= 10m
V T
that is V = constant
T
Relationship between volume and temperature
Lower temperature
Higher temperature, faster molecules, larger volume to keep the
pressure constant
/0C
100
-273
P T
That is P = constant
T
Higher temperature molecules move faster, greater pressure
Relationship between pressure and temperature
Figure 2
Figure 3.1
Figure 3.2
Figure (a)
Figure (b)
State one suitable inference that can be made. [1 mark]
State appropriate hypothesis for an investigation. [1 mark]
Design an experiment to investigate the hypothesis stated in
(b).
