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St. Joseph’s College

F.3 Physics

2006-07 Half-Yearly Examination

Answer ALL Questions in Sections A and B in the answer sheet provided.

In calculations you should show all the main steps in your working.

Unless otherwise specified, numerical answers should be either exact or correct to three significant figures.

Time allowed: 60 Minutes.

Given: The specific heat capacity of water is 4 200 J kg – 1 o C – 1

The specific latent heat of fusion of ice is 3.34 × 10 5 J kg – 1

The specific latent heat of vaporization of water is 2.26 × 10 6 J kg – 1

Section A M. C. Questions (Each carries 2 marks)

1. What is the meaning of “specific heat capacity”?

A. Energy needed to heat up a substance.

B. Energy transferred by heating needed to

raise the temperature of a substance.

C. Energy transferred by heating needed to

raise the temperature of 1kg of the substance

by 1 o C.

D. Energy transferred by heating needed to

raise the temperature of a substance by 1 o C.

2. A mercury-in-glass thermometer was put in

melting ice and boiling water respectively. It is

found that the length of the mercury column is

2.5 cm and 20.0 cm. What is the temperature if

the length of the mercury column is found to be

6.5 cm?

A. 22.9 o C

B. 32.5 o C

C. 37.1 o C

D. 77.1 o C

3. 2 kg of water at 60 o C is mixed with 1 kg of water

at 0 o C. Assume no energy loss, what is the final

temperature of the mixture?

A. 10 o C

B. 20 o C

C. 30 o C

D. 40 o C

4. Which of the following statements about melting

of ice is correct?

A. Energy is released from the ice to the

surroundings.

B. Potential energy of the ice increases during

the melting of ice.

C. Temperature increases during the melting of

ice.

D. The average distance between the molecules

decreases during the melting of ice.

5. Which of the following statements is WRONG?

A. Heat is the energy stored in an object.

B. Heat is the energy flow from one object to

another as a result of difference in

temperature.

C. Internal energy of an object can be increased

when it absorbs heat.

D. Potential energy of an object increases when

it changes from solid state to liquid state.

6. Which of the following substances is a liquid at

50 o C?

substancemelting point

(o C)

boiling point

(o C)

A. W 55 155

B. X –24 120

C. Y 80 216

D. Z -183 -10

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7. A 1 kW heater is immersed into 2 kg of water.

How long does it take to heat up the water from

15 o C to 55 o C?

A. (55 – 15) × 2 × 4200 s

B. 1000

5542002 ×× s

C. 2 × 4200 × (55 – 15) × 1000 s

D. ( )

1000155542002 −××

s

8. When water vaporizes to steam, which of the

following statements is/are correct?

(1) Temperature must be over 100 o C.

(2) Average kinetic energy of water molecules

remains unchanged.

(3) Internal energy of water is increased.

A. (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

9. Two solids which have equal mass and initial

temperature are heated by two identical

heaters.

0Time

TemperatureY

X

The above graph shows their variation of

temperature with time. Which of the following

statements is correct?

A. X has a higher specific heat capacity in solid

state.

B. Y has a higher specific heat capacity in solid

state.

C. X has a higher melting point.

D. Y has a higher specific latent heat of fusion.

10. Water is used in car engines as a coolant because

(1) melting point of water is low.

(2) specific heat capacity of water is large.

(3) specific latent heat of vapourization of water

is large.

A. (1) only

B. (2) only

C. (1) and (2) only

D. (1) and (3) only

11. Four different blocks at 20 o C are heated by

identical heaters. The time taken for each block

to reach to 60 o C is listed below. Which block has

a larger specific heat capacity?

Mass of block / kg Time taken / s

A. 1.2 120

B. 1.5 180

C. 1.5 200

D. 1.2 200

12. The diagram below shows the set-up for

determining the specific heat capacity of water.

to powersupply

heater

thermometer

polystyrenecup

Which of the following is/are necessary to ensure

a more reliable result?

(1) The heater should totally immersed in water.

(2) Glass beaker should be used instead of

polystyrene cup.

(3) A metal cover is placed over the cup.

A. (1) only

B. (2) only

C. (1) and (2) only

D. (1) and (3) only

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Section B Structured-type Questions (Total 36 marks)

1. The power of an oven can be measured by putting a beaker of water in the oven and finding the

temperature rise of the water in a measured time. In such an experiment the observations were as follows:

mass of water = 0.5 kg

initial temperature of water = 20 o C

final temperature of water = 50 o C

time taken for heating = 3 minutes

specific heat capacity of water = 4 200 J kg – 1 o C – 1

(a) How much energy was given to the water? (2 marks)

(b) Determine the power of the oven. (2 marks)

(c) The actual power of the oven is different from that found in (b). Suggest how they are different and

explain your answer briefly. (4 marks)

2. An electric kettle of power 3 kW contains 1.7 kg of water at 20 o C. It takes 3.5 minutes to raise the

temperature of the water to 100 o C.

(a) Calculate

(i) the energy supplied by the heater, (2 marks)

(ii) the energy gained by the water, and (2 marks)

(iii) the energy loss, (1 mark)

during the first 3.5 minutes.

(b) It takes a further 4 minutes to boil 0.23 kg of water away. Calculate

(i) the energy gained by the water in this 4 minutes, and (2 marks)

(ii) the specific latent heat of vaporization of water. (2 marks)

3. Two copper blocks of mass 0.2 kg is heated to 120 o C. One of them is thrown into water of mass 0.15 kg and

the other is thrown into an unknown liquid X of mass 0.22 kg and both of them have an initial temperature

of 22 o C. The final temperature of the water and the copper mixture is 33 o C while that of the liquid and

the copper is 45 o C.

(a) Determine the specific heat capacity of copper. (3 marks)

(b) Hence, estimate the specific heat capacity of the liquid X. (3 marks)

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4. A substance of mass 0.1 kg is heated using a 50 W heater, from –20 o C to about 100 o C. The heating curve

obtained is shown in Figure 1.

-40

0

40

80

Temperature / Co

Time / min4 8 12 16 20 24 28

A

BC

DE

F

Figure 1

(a) What is the melting point and the boiling point of the substance? (2 marks)

(b) Identify the physical states of the substance over the interval BC, CD and DE. (3 marks)

(d) Estimate the specific heat capacity of substance in its liquid state? (3 marks)

(e) Estimate the specific latent heat of fusion of the substance? (2 marks)

(f) Compare the specific latent heat of vaporization of the substance with the specific latent heat of fusion

of the substance, which of them is of greater value? Show your calculation. (3 marks)

– End of the Paper –