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Theory Section: [Total 21Marks]Date: …………Test Unit 10-11

Name: ...………………………………………Paper: PhysicsTime Allowed: 40 Minutes

Code 5054Maximum Marks: 25

Class: I

Unique Science Academy106-A, New Muslim Town, Lahore

Fig. 1.1

Fig. 1.1 shows a domestic heater that is used to heat a room. It contains 16 large bricks 1 each of mass 7.5 kg.

During the night, the bricks are heated from a temperature of 17 °C to 96 °C. The bricks are made from a material that has a specific heat capacity of 2300 J / (kg °C).

(a) Calculate the thermal energy (heat) supplied to the bricks.

thermal energy = ................................................. [3]

(b) During the day, the bricks gradually cool and the stored thermal energy is released to the room. After 7.0 hours, the bricks have cooled to 17 °C.

(i) Calculate the average rate of release of thermal energy to the room during these 7.0 hours.

rate = ................................................. [2]

Dedicated To My Son Mohammad Irtaza Zain [Turn Over]

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(ii) At the beginning of the day, the heater releases thermal energy at a greater rate than later in the day.

Suggest why.

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............................................................................................................................. [2]

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2 (a) Suggest

(i) an example of a change of state resulting from the removal of thermal energy from a quantity of material,

.............................................................................................................................. [1]

(ii) the effect of this change of state on the temperature of the material.

............................................................................................................................. [1]

(b) Define the thermal capacity of a body.

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [2]

(c) A polystyrene cup holds 250 g of water at 20 °C. In order to cool the water to make a cold drink, small pieces of ice at 0 °C are added until the water reaches 0 °C and no unmelted ice is present.

[specific heat capacity of water = 4.2 J / (g °C), specific latent heat of fusion of ice = 330 J / g]

Assume no thermal energy is lost or gained by the cup.

(i) Calculate the thermal energy lost by the water in cooling to 0 °C.

thermal energy lost = ................................................. [2]

(ii) State the thermal energy gained by the ice in melting.

thermal energy gained = ................................................. [1]


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y (iii) Calculate the mass of ice added.

mass of ice = ................................................. [2]

energy = ...........................................................[3]

3 Some sea water has a specific heat capacity of 3900 J / (kg °C) and a boiling point of 100.6 °C.

(i) Calculate the energy required to raise the temperature of 0.800 kg of this sea water from 12.0 °C up to its boiling point. State the equation that you use.

(ii) The energy to raise the temperature in (b)(i) is supplied at the rate of 620 W.

Calculate the time taken to raise the sea water to its boiling point.

time = ...........................................................[2]

1 What is the name given to the amount of energy needed to turn 1 kg of water at 100 °C into steamat 100 °C?

A heat capacity

B latent heat

C specific heat capacity

D specific latent heat


MCQ Section: [Total4Marks]

[Total 9 Marks]

[Total 5 Marks]

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n2 In the experiment shown, the amount of electrical energy used to melt some ice is measured

using a joulemeter.

To find the specific latent heat of fusion of the ice, what must also be measured?

A the mass of water produced by melting ice

B the temperature change of the ice

C the time taken for the ice to melt

D the voltage of the electrical supply

crushed,pure ice

immersionheater

joulemeter

electricitysupply

3 What is a unit of specific latent heat?

A J B J/g C J/ °C D J/(g °C)

4 When ice melts to become water, which force must be overcome?

A the attraction between electrons and the nucleus

B the attraction between the atoms in a molecule

C the force between molecules

D the force of gravity


MCQ Answer Sheet

43

21 A B C D

A B C DA B C DA B C D

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