Download chapter 4 : heat

CHAPTER 4 : HEAT
4.1
Understanding Thermal Equilibrium
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A student is able to:
4.1.1 Explain thermal equilibrium
4.1.2 Explain how a liquid-in-glass thermometer works
* Choose the correct word in the bracket.
1.
*( Heat , Temperature ) is the degree of hotness of a body.
2.
*( Heat , Temperature ) is a form of energy.
3.
A hot body has a …………… temperature where as a cold body has a
………………… temperature.
4.
The SI unit for heat is …………….
5.
The SI unit for temperature is …………
6.
Temperature is a *( base , derived ) quantity.
7.
Heat is a *( base , derived ) quantity.
8.
The figure shows two metal blocks in thermal contact.
A
30 0 C
(a)
(b)
(c)
(d)
(e)
B
80 0 C
Energy is transferred from *( A , B ) to *( A , B ) at a faster rate.
Energy is transferred from *( A , B ) to *( A , B ) at a slower rate.
Temperature A will *( increase , decrease ).
Temperature B will *( increase , decrease ).
The net heat will flow from *( A , B ) to *( A , B ) until they are at the
same temperature.
9.
Two bodies are said to be in thermal equilibrium when :
(a) they are at the *( zero , same ) temperature.
(b) the net rate of heat flow between the two bodies is *( zero , same ).
10.
Temperature is measured by a ………………..with works with the principle of
……………………….
11.
Name the physical property (thermometric property) which varies with
temperature used in a liquid-in-glass thermometer.
………………………..
1
12.
The liquids commonly used in liquid-in-glass thermometers are ……………….
and ………………….
13.
Comparison of mercury and alcohol as a liquid-in-glass thermometer.
Mercury
14.
Alcohol
Freezing point :
Boiling point :
Freezing point :
Boiling point :
It *(wet, does not wet) the tube.
It *(wet, does not wet) the tube.
*(Opaque , colourless)
Easy to read.
It is *(poisonous, safe liquid).
*(Opaque , colourless)
It needs to be dyed.
It is *(poisonous, safe liquid).
It is *(cheap, expensive).
It is *(cheap, expensive).
Conducts heat well, responds faster
to temperature changes.
Responds more slowly then mercury.
Complete the following table concerning a liquid-in-glass thermometer.
Features
Explanation
The glass bulb is thin.
The bulb is made small.
The bore of the capillary tube is
narrow and uniform.
The walls of the long tube above
the bulb are made thick
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15.
Temperature of liquid,  
l  l0
 100 0 C ,
l100  l0
Where, l 0 = length of mercury at …………….. point.
l100 = length of mercury at …………….. point.
l = length of mercury at  point.
16.
An uncalibrated thermometer is attached to a centimetre scale and reads
5.0 cm in pure melting ice and 30.0 cm in steam. When the thermometer is
immersed in the liquid y, the length of the mercury column is 15.0 cm. What
is temperature of liquid y?
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4.2
Understanding Specific Heat Capacity
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A student is able to:
4.2.1 Define specific heat capacity I
4.2.2 State that c= Q
mθ
4.2.3
4.2.4
4.2.5
4.2.6
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 substance is the
quantity of heat needed to increase the temperature of a mass of 1 kg by
1 0 C or 1 K.
2.
Specific heat capacity, c =
Q
m
Where, m = …………………
Q = ……………………………………………………
 = …………………………………………………….
3.
The unit of specific heat capacity is ………………….
4.
The quantity of heat absorbed or lost from a body is given by, Q = ……………
5.
How much heat energy is required to raise the temperature of 1.5 kg of water
from 30 0 C to its boiling point ? The specific heat capacity of water is 4200
J kg 1 0 C 1 .
6.
Conversion of energy
(a)
Electrical energy from heater transformed into heat energy.
……… = m c 
(b)
Potential energy of a falling object transformed into heat energy.
……… = m c 
(c)
Kinetic energy of a moving object is transformed into heat energy
when it is stopped due to friction.
……… = m c 
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7.
A 700 W electric heater is used to heat 2 kg of water for 10 minutes.
Calculate the temperature rise of the water. The specific heat capacity of
water is 4200 J kg 1 0 C 1 .
8.
A copper block weighing 2 kg is dropped from a height of 20 m. What is the
rise in temperature of the copper block after it hits the floor. The specific heat
capacity of copper is 400 J kg 1 0 C 1 .
9.
A bullet traveling at 60 m s 1 hit a sand bag. The temperature of the bullet
rises by 4.5 0 C. Calculate the specific heat capacity of the bullet.
10.
100 g of hot water at 90 0 C is mixed with 200 g of cold water at 30 0 C.
Assuming that no heat is lost, calculate the final temperature of the mixture.
11.
Complete the following table.
Material has a high specific heat
capacity
It takes a longer time to be heated.
Material has a low specific heat
capacity
It lose heat easily.
It is a heat insulator.
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4.3
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Understanding Specific Latent Heat
A student is able to:
4.3.1 State that transfer of heat during a change of phase does not cause a change
in temperature
4.3.2 Define specific latent heat (l)
4.3.3 State that l = Q
m
4.3.4
4.3.5
4.3.6
Determine the specific latent heat of fusion
Determine the specific latent heat of vaporization
Solve problems involving specific latent heat
1.
Matter exists in three states, that is solid, ……………. and ………….. .
2.
The heat released or absorbed at constant temperature during a change of
state of matter is known as ……………….. .
3.
Latent heat is released
……………
Melting
Solid
Gas
………………
………
condensation
……………………………
4.
Specific latent heat of …………….. is the quantity of heat that is needed to
change 1 kg of a substance from solid state to liquid state, without a change
in temperature.
5.
Specific latent heat of …………….. is the quantity of heat that is needed to
change 1 kg of a substance from liquid state to vapour state, without a
change in temperature.
6.
Specific latent heat, L =
Q
m
Where, Q = latent heat absorbed or released by the substance
m = mass of the substance.
7.
The SI unit for specific latent heat is ………………. .
8.
What is the quantity of heat required to melt 2 kg of ice at 0 0 C ? Specific
latent heat of fusion of ice = 336000 J kg 1 .
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9.
Temperature /
0
C
F
90
B
C
5
15
D
E
20
35 Time/minute
70
30
0
A
Figure shows the temperature- time graph for a substance, S of mass 2.0 kg,
being heated using a 500 W heater.
(a)
Based on the graph state the physical condition of substance, S in
(i)
AB : ……………………………………………………………..
(ii)
BC : ……………………………………………………………..
(iii)
CD : ……………………………………………………………..
(iv)
DE : ……………………………………………………………..
(b)
Melting point : ………………………………………………………….
(c)
Boiling point : ……………………………………………………………
(d)
By using kinetic theory, explain why the temperature of substance, S
in AB is increasing.
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
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(e)
By using kinetic theory, explain why the temperature of substance, S
is constant in BC even though heat is still been supplied to it.
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
…………………………………………………………………………………
(f)
Calculate the specific heat capacity of the substance in solid state.
(g)
Calculate the specific latent heat of vaporization of substance, S.
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4.4
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Understanding The Gas Laws
A student is able to:
4.4.1 Explain gas pressure, temperature and volume in terms of the behavior of gas
molecules
4.4.2 Determine the relationship between pressure and volume at constant
temperature for a fixed mass of gas ie Pv = constant
4.4.3 Determine the relationship between volume and temperature at constant
pressure for a fixed mass of gas ie
V/T = constant
4.4.3 Determine the relationship between pressure and temperature at constant
volume for a fixed mass of gas ie
p/T = constant
4.4.4 Explain about zero
4.4.5 Explain the absolute/Kelvin scale of temperature
4.4.6 Solve problems involving the pressure, temperature and volume of a fixed
mass of gas
Complete the table below about gas laws’
1.
Boyle’s Law
Charles’ Law
1
P
V
Constant Variable :
1. Mass of gas
2.
Boyle’s law states that the
pressure of a fixed mass of
gas is inversely
proportional to its volume
at constant temperature.
P
0
V
P
P T
Constant Variable :
1. Mass of gas
2. Pressure of gas
Charles’ law states that
Constant Variable :
1. Mass of gas
2.
Pressure law states that
V
P
T/ 0 C
0
V
0
1
V
0
T/ 0 C
P
0
T/K
9
0
T/K
P
V
0
P
P
V
0
V
V
T
0
2.
P
T
V
T
V
P
P
T
0
T
0
T
Figure (a) show 18 cm of air column trapped in a capillary tube by 4 cm of
mercury. If the glass tube is inverted, what is the length, L, of the air column
trapped in the capillary tube?
(Atmospheric pressure = 76 cm Hg)
4 cm
L
18 cm
air
air
4 cm
(a)
3.
0
(b)
An air bubble released by a diver has a volume of 4.0 cm 3 at depth of 15 m.
What is the volume of the bubble at a depth of 10 m?
(Atmospheric pressure = 10 m water)
10
4.
The value -273 0 C is equivalent to …… K. This temperature is known as the
………………………………………
5.
Convert 27 0 C to its equivalent temperature in Kelvin.
6.
Convert 330 K to its equivalent temperature in degrees Celsius.
7.
The volume of a gas is 5 cm 3 at 27 0 C. The gas is heated at fixed pressure
until the column becomes 6 cm 3 . Calculate the final temperature of the gas.
8.
A gas of volume 20 cm 3 at 47 0 C is heated until its temperature becomes
87 0 C at constant pressure. What is the final volume of the gas?
9.
Before a journey from Parit Buntar to Ipoh, the air in a car tyre has a pressure
of 200 kPa and a temperature of 27 0 C. After the journey, the air pressure in
the tyre is 220 kPa. What is the temperature of the air in the tyre after the
journey?
10.
The pressure of gas in a light bulb is 50.5 kPa at 30 0 C. Calculate the
pressure of the gas when the temperature inside the bulb rises to 87 0 C after
the bulb is lighted up.
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