CHAPTER 4: HEAT
SPM 2003,Section C, No. 3 [20 Marks]
1 You are representing the country in carrying out a research project on the weather at the
North Pole. The surrounding temperature is between -400C to -80C. One item of the
equipment to be taken for your research is a thermometer.
(a) State the principle used in a liquid-glass thermometer.
[1 mark]
(b) State how a liquid-glass thermometer can be used to measure the body temperature of
a sick person. Explain heat transfer that takes place at each stage of measurement.
[4 marks]
(c) The table shows the characteristics of six types of thermometer P, Q, R, S, T and U.
Thermometer
Liquid
used
Glass
walled
bulb
Diameter of
capillary
tube
Glass-bore
stem
P
mercury
thin
big
thick and
curved
Q
mercury
thick
small
thin and plane
R
mercury
thin
small
thin and curve
S
alcohol
thick
big
thick and plane
T
alcohol
thin
small
thick and
curved
U
alcohol
thick
small
thin and plane
Additional information:
Freezing point of mercury = -390C
Freezing point of alcohol = -1120C
Cross-section
Boiling point of mercury = 3600C
Boiling point of alcohol = 780C
Based on the table above
(i)
(ii)
Explain the suitable characteristics of the thermometer so that it can be used to
measure temperature at the North Pole.
Decide which thermometer is most suitable to be taken for your research and
give reasons.
[10 marks]
47
(d) A thermometer which is not calibrated has a mercury column of length 8.0 cm when the
temperature is 00C and 20.0 cm when the temperature is 1000C. The mercury column
is 5.0 cm when put in liquid X.
(i)
(ii)
Determine the temperature of liquid X in Kelvin
State a thermometric property used when making of a thermometer.
[5 marks]
SPM 2004 , Section C , No. 11 [20 Marks]
2
(a)Figure 3.1 shows a food container used for keeping food warm. The container is able to
maintain the temperature of food for a long time. The container can be moved from one
place to another.
Figure 3.1
Table 3.1 shows the characteristics of materials which could be used to make the food
container.
Characteristic
Specific heat
Melting Point /
Thermal
Density / kg m-3
capacity / J kg-1
0
C
conductivity
0 -1
C
Material
P
2 710
660
910
High
Q
910
27
1 600
Low
R
1 050
240
1 300
Low
S
2 600
1 200
670
Low
T
3 800
2 020
800
HIgh
(i) What is meant by melting point ?
[1 mark]
(ii) Your are asked to investigate the characteristics of the material in Table 3.1 Which
could be used to make the food container as in Figure 3.1
Explain the suitability of each characteristics in Table 3.1 and hence, determine
Which material is most suitable to be used to make the food container.
Justify your choice.
[10 marks]
(b) 500 g of hot water at 90 0C is poured into a glass and left to cool down to room
temperature at 30 0C.
(i) Sketch the temperature-time graph for the cooling process of the hot water. Use
your graph to explain this process.
[4 marks]
(ii) Calculate the quantity of heat lost from the hot water. The specific heat capacity of
water is 4 200 J kg-10C-1.
[2 marks]
48
(iii) Hot water is poured into a glass which has a small crack. It is observed that the
size of the crack increases.
Explain this observation.
[3 marks]
SPM 2006 Section C, No. 11 [20 Marks]
3
(a)(i) What is meant by specific latent heat of vaporization?
[1 mark]
(ii)Explain why someone who is sweating feels cool when he is under a rotating fan.
[4 marks]
(b) A solid substance, of mass 0.05 kg, is heated using an immersion heater of 240 V,0.1
kW. Diagram 11.1 shows the heating curve of the solid.
Temperature / 0C
Time /
min
Diagram 11.1
Calculate
(i) The specific latent heat of fusion of the substances,
(ii) The specific latent heat capacity of the substances in liquid state.
[5 marks]
(c) Your are asked to investigate the features of cooling material and the design of a car
engine radiator as in Diagram 11.2.
Explain the suitability of each features in Diagram 11.2 and then determine the most
suitable car engine radiator to be used.
Give a reason for your choice.
[10 marks]
49
The features of cooling liquid
P


Boiling point 100 0C
Specific heat capacity 4 200 J
kg-1 C-1
The features of cooling liquid
Q


Boiling point 100 0C
Specific heat capacity 4 200 J
kg-1 C-1
The features of cooling liquid
R


Boiling point 100 0C
Specific heat capacity 4 200 J
kg-1 C-1
The features of cooling liquid
S


Boiling point 78 0C
Specific heat capacity 2 450 J
kg-1 C-1
The features of cooling liquid
T


Boiling point 78 0C
Specific heat capacity 2 450 J
kg-1 C-1
50