CHAPTER 4 : HEAT

SPM 2003,Section A, No. 2 [5 Marks]

1 / The block P and Q in Figure 2 have the same mass. They are immersed in boiling water for along time. P and Q are then transferred into beakers X and Y respectively as shown in Figure 3.

Figure 2 Figure 3
The mass of water in both beakers X and Y is 0.25 kg and the initial temperature of the water in each beaker is the same.
Specific heat capacity of P is 900 J kg-10C-1
Specific heat capacity of Q is 390 J kg-10C-1
Specific heat capacity of water is 4 200 J kg-10C-1
(a)(i) State the initial temperature of the blocks
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[1 mark]
(ii) Why is the final temperature of the water in beaker X is higher than that in beaker Y?
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[1mark]
(b)(i) Calculate the rise in temperature of the water in beaker Y if block Q release 8 400 J
of heat energy.
[2 marks]
(ii) State one assumption which you have made in (b)(i)
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[1 mark]

SPM 2005, Section A , No. 4 [7 Marks]

2 / (a)Sweating is one of the ways our body maintains the body temperature of about 370C. Sweat is largely made up of water and it comes from sweat glands as shown in Figure 4.1

Figure 4.1
When sweat evaporates, it takes heat away from our body.
(i)What is meant by evaporation ?
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[1 mark]
(ii)Using kinetic theory of matter, explain how evaporation takes away heat from our
body.
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[2 marks]
(b)State two environmental factors that affect the rate of evaporation of sweat.
1......
2......
[2 marks]
(c)While playing badminton, 0.05 kg of sweat was evaporated from Ahmad’s body.
Calculate the quantity of heat lost from his body due to the evaporation.
The latent heat of vaporisation of sweat is 2.3 x 106 J kg-1.
[2 marks]

SPM 2006 Section A, No. 2 [5 Marks]

3 / Diagram 2 shows a mercury thermometer which has not been calibrated

Diagram 2
(a)(i) State the physical change in the mercury when the temperature increases.
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[1 mark]
(ii) Why is mercury used in the thermometer?
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[1 mark]
(b) The length of the mercury column in the thermometer is 2.6 cm at 0 0C and 22.6 cm at
100 0C.
(i) What is the difference in the lengths of the mercury columns at 0 0C and at 100 0C ?
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[1 mark]
(ii) When the thermometer is placed in hot oil, the length of the mercury column is
16.9 cm .
Calculate the temperature of the hot oil.
[2 marks]

SPM 2007, Section A, No. 3 [7 Marks]

4 / Diagram 3.1 shows the change of phase when 1 kg ice is converted into steam.
R S T U

Diagram 3.1
Q1, Q2 and Q3 are the heat energies absorbed during the heating process.
(a)Name the heat energy, Q, which is absorbed from R to S.
…………………………………………………………………………………………......
[1 mark]
(b)State one reason why the temperature R and S is the same even though heat is supplied.
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[2 marks]
(c)Calculate the heat energy, Q2, which is absorbed from S to T.
[The specific heat capacity of water, C = 4 200 J kg-10C-1]
[2 marks]
(d)Sketch the graph of temperature against time on Diagram 3.2 to show the change of phase from R to U.
Temperature /0C
Diagram 3.2
[2 marks]

SPM 2008, Section A, No. 8 [12 Marks]

5 / Diagram 8.1 shows a 500 W electric heater being used to heat a beaker of water on a compression balance.

Diagram 8.1
(a)State the energy change involved when using the heater to heat the water.
……………………………………………………………………………………………...
[1 mark]
(b)The mass of water is 0.5 kg and the specific heat capacity of water is 4 200 J kg-10C-1. The initial temperature of the water is 30 0C.
Calculate the energy absorbed by the water to reach its boiling point.
[ 2 marks]
(c)When the water is boiling, the reading of the compression balance decreases by 0.0125 kg in 60 s.
Calculate the specific latent heat of vaporization of the water.
[ 2 marks]
(d)Q, R and S are three different hot plates. These hot plates are used to heat ‘roti canai’.
Table 8 shows the characteristics of each plate.
Hot Plates / Spesific Heat Capasity, c
J kg-10C-1 / Mass, m
kg / Power, P
W
Q / 390 / 3.0 / 600
R / 900 / 2.5 / 1 200
S / 400 / 4.0 / 900
Table 8
The initial temperature of each plate is 30 0C.
The plates are ready to use when their temperature reaches 200 0C.
Calculate the time taken to reach 200 0C for each plate.
(i)Plat Q
(ii)Plat R
(iii)Plat S
[5 marks]
(e)(i) Based on the answer in 8(d), which plate is the most suitable for heating ‘roti canai’.
…………………………………………………………………………………………………
[1 mark]
(ii) State one reason for the answer in 8(e)(i).
………………………………………………………………………………………………......
[1 mark]

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