Heat, Change of State, and Vapours Generix Content - Heat, Change of State, and Vapours
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JAMB questions for "Physics :: Heat, Change of State, and Vapours"
Q1
The thermos flask is designed to
A
store hot tea or water
B
prevent heat loss or gain by conduction , convection and radiation
C
prevent heat gain by conduction, convection and radiation
D
prevent heat loss by conduction, convection and radiation
E
Q2

106 J of heat is required to boil off completely 2 kg of a certain liquid. Neglecting heat lost to the surroundings, the latent heat of vapourization of the liquid is

A

5.0 x 105 J kg-1

B

2.0 x 105 J kg-1

C

5.0 x 106 J kg-1

D

2.0 x 105 J kg-1

E
Q3
The process whereby a liquid turns spontaneously into vapour is called
A
evaporation
B
regelation
C
boiling
D
sublimation
E
Q4
Tea pots are often silver-coated to prevent heat loss by
A
conduction only
B
convection only
C
convection and conduction
D
E
Q5

A 50W electric heater is used to heat a metal block of mass 5kg. If in 10 minutes a temperature rise of 12°C is achieved, the specific heat capacity of the metal is

A

400 J kg-1 K-1

B

500 J kg-1 K-1

C

390 J kg-1 K-1

D

130 J kg-1 K-1

E
Q6

A 2000 W electric heater is used to heat a metal object of mass 5 kg  initially at 10°C . If a temperature rise of 30°C is obtained after 10min, the heat capacity of the material is

A

1.2 x 104 J °C-1

B

6.0 x 104 J° C-1

C

8.0 x 103 J° C-1

D

4.0  x 104 J° C-1

E
Q7
Blowing air over a liquid aids evaporation by
A
increasing its temperature
B
increasing its surface area
C
decreasing its density
D
decreasing its vapour  pressure
E
Q8
The time rate of loss of heat by a body is proportional to the
A
temperature of its surrounding
B
temperature of the body
C
difference in temperature between the body and its surroundings
D
ratio of the temperature of the body to that of it surroundings
E
Q9

A metal of mass 0.5 kg is heated to 100°C and then transferred to a well-lagged calorimeter of heat capacity 80 JK-1 containing water of heat capacity 420 JK-1 at 15°C. If the final steady temperature of the mixture is 25°C, find the specific heat capacity of the metal

A

92 J kg-1 K-1

B

133 J kg-1 K-1

C

286 J kg-1 K-1

D

877 J kg-1 K-1

E
Q10
The main reason for making the cover of a vacuum flask airtight is to prevent heat loss by
A
conduction
B
evaporation
C
D
convection
E
Q11

A piece of substances of specific heat capacity 450 Jkg-1 K-1 falls through a vertical distance of 20m from rest. Calculate the rise in temperature of the substance on hitting the ground when all its energies are converted into heat.

A

2°C/9

B

4°C/9

C

9°C/4

D

9°C/2

E
Q12

Calculate the mass of ice that would melt when 2kg of copper is quickly transferred from boiling water to a block of ice without heat loss

A

8/33 Kg

B

33/80 kg

C

80/33 kg

D

33/8 kg

E
Q13

A gas has a volume of 100 cm3 at 27°C . If it is heated to temperature T untill a final volume of 120 cm3 is attained, calculate T.

A

33 °C

B

60°C

C

87°C

D

114°C

E
Q14

A 500 W heater is used to heat 0.6 kg of water from 25°C to 100°C in t1 seconds . If another 1000 W heater is used to heat 0.2 kg of water from 10°C in t2 seconds, find t1/t2

A

50

B

5

C

5/4

D

1/5

E
Q15

How many grams of water at 17°C must be added to 42g of ice at 0°C to melt the ice completely?

A

200 g

B

300 g

C

320 g

D

400 g

E
Q16
A vapour is said to be saturated when
A
more molecules return to the liquid than the amount that left it
B
a dynamic equlibrium exists between the molecules of the liquid and vapour molecules at a given temperature
C
the vapour pressure is equal to the atmosphere pressure
D
all molecules are moving with same speed in all directions at a given temperature
E
Q17

The correct cooling curve for a molten substance such as naphthalene is represented by

A
B
C
D
E
Q18
What happens when a certain quantity of pure ice is completely changed to water at 0°C?
A
Latent heat is absorbed, the mass remains constant and the volume decreases
B
Latent heat is given out, the mass remains constant and the volume decreases
C
Latent heat is given out, the mass increases and the volume remains constant
D
Latent heat is absorbed, the mass decreases and the volume increases
E
Q19
An electric kettle with negligible heat capacity is rated at 2 000W. If 2.0 kg of water is put in it, how long will it take the temperature of water to rise from 20°C to 100°C ?
A
420 s
B
336 s
C
168 s
D
84 s
E
Q20
A quantity of ice at -- 10°C is heated until the temperature of the heating vessel is 90°C. Which of the following constants  is NOT required to determine  the quantity of heat supplied to the vessel?
A
Specific heat capacity of ice
B
Specific heat capacity of water
C
Specific latent heat of fussion
D
Specific latent heat of vapourization
E
Q21
An electric current of 2 amperes flows in a hearing coil of resistance 50 ohms for 3 minutes 20 seconds. Determine the heat produced .
A
0.5 kJ
B
8.0 kJ
C
20. 0 kJ
D
40.0k J
E
Q22

When 100 g of liquid L1 at 78°C was mixed with Xg of liquid L2 at 50°C, the final temperature was 66°C. Given that the specific heat capacity of L2 is half that of L1, find X

A

50 g

B

100 g

C

150 g

D

200 g

E
Q23

Heat is supplied to a test tube containing 100g of ice at its melting point. The ice melts completely in 1 min. What is the power rating of the source of heat?  (Latent heat of fusion of ice = 336 Jg -1)

A

336 W

B

450 W

C

560 W

D

600 W

E
Q24
If a room is saturated with water vapour, the temperature of the room must be
A
at 0°C
B
above the dew point
C
at 100°C
D
below or at the dew point
E
Q25
Two similar kettles containing equal masses of boiling water are placed on a table. If the surface of one is highly polished and the surface of the other is covered with soot, which of the following observations is correct?
A
The two kettles will cool down at the same rate
B
The polished kettle cools down more quickly by conduction
C
The kettle covered with soot-cools down more quickly because it is a good radiator of heat
D
The kettle covered with soot cools down more quickly by the process of heat convection
E
Q26

How much heat is absorbed when a block of copper of mass 0.05 kg and specific heat capacity 390 J kg-1 K-1 is heated from 20°C to 70°C ?

A

3.98 X 10-1 J

B

9.75 X 102 J

C

3.98 X 103 J

D

9.75 X 103 J

E
Q27
A block of ice floats on water inside a container . If the block of ice gets completely melted, the level of water in the container will
A
increase
B
remain the same
C
decrease
D
first decrease and then increase
E
Q28
The space between the double glass walls of a thermos flask is evacuated and the two surfaces facing the evacuated space are silvered. The residual source of heat loss tales place by
A
convection
B
C
conduction through the stopper and the glass
D
conduction across the walls
E
Q29

What is the difference in the amount of heat given out by 4 kg of stream and 4 kg of water when both are cooled from 100°C to 80°C?  ( The specific latent heat of stream is 2,260,000 J kg-1 specific heat capacity of water is 4200 J kg-1 K -1 )

A

42 00 J

B

2 260 000J

C

9 040 000J

D

9 380 000 J

E
Q30

How long does it take a 750-W heater to raise th temperature of 1 kg of water from 20°C to 50°C? ( Specific heat capacity of water = 4200 J kg-1 K-1 )

A

84 s

B

112 s

C

168 s

D

280 s

E
Q31
The saturated vapour pressure of a liquid increases as the
A
volume of the liquid increases
B
volume of the liquid decreases
C
temperature of the liquid increases
D
temperature of the liquid decrease
E
Q32
A room is heated by means of a charcoal fire. All occcupants of the room standing away from the fire is warmed mainly by
A
convection
B
C
conduction
D
reflection
E
Q33

1 kg of copper is transfered quickly from boiling water to a block of ice. Calculate the mass of ice melted, neglecting heat loss.  [ Specific heat capacity of copper = 400 J kg-1 K-1 and latent heat of fusion of ice] = 333 X 103 J kg-1

A

60 g

B

67 g

C

120 g

D

133g

E
Q34
Which of the following statements are correct? I. Land and sea breezes are natural convection currents II. Convection may occur in liquids or gases but not in solids III. The vacuum in a thermos flask prevents heat loss due to convection only
A
I and II only
B
II and III only
C
I and III only
D
I, II and III
E
Q35

Which of the following correctly represents the variation of the saturated vapour pressure of water with temperature?

A
B
C
D
E
Q36

An electric heater is used to melt a block of ice mass 1.5kg. If the heater is powered by a 12 V battery and a current of 20A flows through the coil, calculate the time taken to melt the block of ice at 0°C. ( Specific latent heat of fussion of ice = 336 X 103 J kg-1 )

A

76.0 min

B

35.0 min

C

21.0 min

D

2.9 min

E
Q37

Which of the following graphs clearly illustrates the temperature change which takes place as a piece of ice at -10°C is heated slowly?

A
B
C
D
E
Q38
The amount of heat needed to raise the temperature of 10kg of copper by 1K is its
A
specific heat capacity
B
heat capacity
C
latent heat
D
internal energy
E
Q39
A tap supplies water at 25o C while another supplies water at 75°C. If a man wishes to bathe with water at 40°C, the ratio of the mass of cold water to the mass of hot water required is
A
1:3
B
15:8
C
7:3
D
3:1
E
Q40
When heat is applied to one end of a metal rod, the molecules at the other end soon begin to vibrate with greater amplitude than before because heat has been transfered by
A
B
convection
C
conduction
D
evaporation
E
Q41

22,000J of heat is required to raise the temperature of 1.5kg of paraffin from 20°C to 30°C . Calculate the specific heat capacity of paraffin

A

1466J kg-1 °C-1

B

2933J kg-1 °C-1

C

4400J kg-1 °C-1

D

5866J kg-1 °C-1

E
Q42

Calculate the amount of heat required to covert 2kg of ice at -2°C to water at 0°C. ( specific heat capacity of ice = 2090J kg-1 °C-1, specific latent heat of fussion of ice = 333kj kg-1 )

A

666J

B

8360J

C

666, 000J

D

674,360J

E
Q43
In which of the following are the substances arranged in descending order of their thermal conductivities?
A
Copper, steel, glass
B
Steel, copper, glass
C
Steel, glass, copper
D
Copper, glass, steel
E
Q44
The vacuum in a thermo flask helps to reduce heat transfer by
A
B
convection and conduction
C
D
E
Q45
Which of the following phenomena explains the fact that a house whose roof is coated with white paint will be cooler in the hot season than one coated with black paint?
A
Conduction
B
Convection
C
Refraction
D
Reflection
E
Q46
The mode of heat transfer which does not require a material medium is
A
conduction
B
C
convection
D
propagation
E
Q47

The specific latent heat of fusion of lead is the amount of heat required to

A

melt lead at its melting point

B

heat a unit mass of lead through 1° C

C

change the state of a unit mass of lead at its melting point

D

change the state of a unit mass of lead at its boiling point

E
Q48
Which of the following is common to evaporation and boiling? They
A
take place at any temperature
B
are surface phenomena
C
involve change of state
D
take place at a definite pressure
E
Q49
Which of the following properties makes metals ideal for cooking utensils ?
A
High co efficient of expansion
B
Good conduction of heat
C
Low specific heat capacity
D
E
Q50
When two objects P and Q are supplied with the same quality of heat , the temperature change in P is observed to be twice that of Q. The mass of P is half that of Q. The ratio of the specific heat capacity of P to Q is
A
1:4
B
4:1
C
1:1
D
2:1
E
Q51
In an experiment in which molten naphthalene is allowed to cool, the cooling curve in Fig 5 was obtained. The temperature 800 is known as the
A
cooling temperature
B
boiling point
C
melting point
D
vaporization point
E
Q52

Two liquids, P at a temperature of 20°C and Q at a temperature of 80°C have specific heat capacities of 1.0 J kg-1 °C-1 and 1.5 J kg-1 °C-1 respectively . If equal masses of P and Q are mixed in  a lagged calorimeter, then the equilibrum temperature is

A

44°C

B

50°C

C

56°C

D

60°C

E

70°C

Q53

Two thermos flasks of volume Vx any Vy are filled with liquid water at an initial temperature of 0°C. After some time the temperature were found to be θx, θy respectively. Given that  Vx/Vy= 2 and θx/θy=1/2 the ratio of the heat flow into the flasks is

A

1/4

B

1/2

C

4

D

1

E

2

Q54
A good calorimeter should be of
A
low specific heat capacity and low heat conductivity
B
low specific heat capacity and high heat conductivity
C
high specific heat capacity and low heat conductivity
D
high specific heat capacity and low heat conductivity
E
dull surface and low heat conductivity
Q55
Which of the following statements is NOT correct?
A
Boiling occurs when the saturated vapour pressure of the liquid involved equals the external pressure
B
Both the boiling point and the saturated vapour pressure of a given liquid depend on the external pressure
C
The saturated vapour pressure rises with increase in temperature
D
The saturated vapour pressure is independent of the volume available for the vapour
E
it is possible to boil water at a lower temperature than 100°C at high altitude
Q56

All the heat generated in a 5 Ω resistor by 2 A flowing for 30 seconds is used to evaporate 5 g of a liquid at its boiling point. Which of the following is the correct value of the specific latent heat of the liquid?

A

120 J

B

60 J g-1

C

120 J g-1

D

1500 J

E

1500 J g-1

Q57
Dewpoint is the temperature at which water vapour in the atmosphere
A
turns into steam
B
solidifies into ice pellets
C
first condenses into liquid form
D
is just suficient to cause cooling
E
has a relative humidity of fifty per cent
Q58
If a solid changes directly into a gas when heat is applied the process is called
A
vapourization
B
evaporation
C
sublimation
D
ionization
E
conversion
Q59

Heat is supplied uniformly at the rate of 100 W to 1.0 X 10-2 kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5°C then the specific heat capacity of the liquid is

A

2.0 X 102 Jkg-1 K-1

B

2.0 X 102 JKg-1

C

4.0 X 104 JKg-1 K-1

D

4.0 X 104 JKg-1  K-1

E

8.4 X 102 JKg-1  K-1

Q60
The specific latent heat of vapourization of a substance is always
A
less than specific latent heat of fussion
B
greater than its specific heat of fussion
C
equal to its specific latent heat of fussion
D
all of the above depending on the nature of substance
E
none of the above