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Secondary 3 Physics Thermal Physics Quiz
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Questions
Secondary 3 Physics Quiz - Thermal Physics
Name: ___________________________
Class: ___________________________
Date: ___________________________
Score: _________ / 40
Duration: 50 minutes
Total Marks: 40
Instructions:
- Answer ALL questions.
- Write your answers in the spaces provided.
- Show all working clearly for calculation questions.
- The number of marks for each question is shown in brackets [ ].
- You may use a calculator where necessary.
Section A: Multiple Choice Questions (10 marks)
Questions 1–10: Choose the most correct answer. Each question carries 1 mark.
1. Which of the following is the SI unit of heat capacity?
A. J kg⁻¹ °C⁻¹
B. J °C⁻¹
C. J kg⁻¹
D. W °C⁻¹
Answer: ___________ [1]
2. A metal block is heated from 25 °C to 85 °C. What is the temperature change in kelvin?
A. 60 K
B. 110 K
C. 358 K
D. 333 K
Answer: ___________ [1]
3. During boiling, the temperature of a liquid remains constant because the heat energy supplied is used to
A. increase the kinetic energy of the molecules.
B. overcome the intermolecular forces between molecules.
C. increase the pressure of the gas above the liquid.
D. expand the volume of the liquid.
Answer: ___________ [1]
4. Which process of thermal energy transfer does NOT require a medium?
A. Conduction
B. Convection
C. Radiation
D. Diffusion
Answer: ___________ [1]
5. Two objects, X and Y, are in thermal contact. Heat will flow from X to Y when
A. X has more mass than Y.
B. X has a higher temperature than Y.
C. X has a greater heat capacity than Y.
D. X has a larger volume than Y.
Answer: ___________ [1]
6. The specific heat capacity of a substance is defined as the amount of thermal energy required to
A. raise the temperature of the substance by 1 °C.
B. raise the temperature of 1 kg of the substance by 1 °C.
C. melt 1 kg of the substance at its melting point.
D. boil 1 kg of the substance at its boiling point.
Answer: ___________ [1]
7. A shiny silver surface is a poor __________ of thermal radiation.
A. absorber and poor emitter
B. absorber and good emitter
C. reflector and poor absorber
D. transmitter and good emitter
Answer: ___________ [1]
8. In which state of matter does conduction occur most efficiently?
A. Gas
B. Liquid
C. Solid
D. All states equally
Answer: ___________ [1]
9. A 2 kg block of aluminium (specific heat capacity = 900 J kg⁻¹ °C⁻¹) absorbs 18 000 J of thermal energy. What is the temperature rise of the block?
A. 5 °C
B. 10 °C
C. 20 °C
D. 40 °C
Answer: ___________ [1]
10. During condensation, a gas
A. gains thermal energy and its temperature increases.
B. loses thermal energy and its temperature decreases.
C. gains thermal energy but its temperature remains constant.
D. loses thermal energy but its temperature remains constant.
Answer: ___________ [1]
Section B: Short Answer and Structured Questions (20 marks)
Questions 11–16: Answer in the spaces provided.
11. Define the following terms:
(a) Specific heat capacity.
_____________________________________________________________________________ [2]
(b) Specific latent heat of fusion.
_____________________________________________________________________________ [2]
12. Explain, in terms of molecular behaviour, why the temperature of a substance remains constant during melting.
_____________________________________________________________________________ [3]
13. State two differences between boiling and evaporation.
| Boiling | Evaporation | |
|---|---|---|
| Difference 1 | _________________________ | _________________________ |
| Difference 2 | _________________________ | _________________________ |
[2]
14. A student heats 0.5 kg of water using an electric heater. The temperature of the water rises from 20 °C to 100 °C.
(a) Calculate the thermal energy absorbed by the water.
(Specific heat capacity of water = 4 200 J kg⁻¹ °C⁻¹)
Working: _______________________________________________________________
Answer: _______________________ J [2]
(b) If the heater has a power rating of 500 W, calculate the time taken to heat the water, assuming no energy is lost to the surroundings.
Working: _______________________________________________________________
Answer: _______________________ s [2]
15. The diagram below shows a metal rod with wax blobs attached at equal intervals. One end of the rod is heated with a Bunsen burner.
Wax blob: A B C D E
| | | | |
======================================== ← Metal rod
↑
Bunsen burner
(a) In which direction does thermal energy travel along the rod?
_____________________________________________________________________________ [1]
(b) Explain why wax blobs near the heated end melt first.
_____________________________________________________________________________ [2]
(c) Name the process by which thermal energy is transferred along the rod.
_____________________________________________________________________________ [1]
16. Explain why the metal handle of a saucepan becomes hot even though it is not in direct contact with the stove. Refer to the process of thermal energy transfer in your answer.
_____________________________________________________________________________ [2]
Section C: Longer Response and Application Questions (10 marks)
Questions 17–20: Answer in the spaces provided. Show all working for calculation questions.
17. A 0.8 kg block of copper (specific heat capacity = 385 J kg⁻¹ °C⁻¹) at an initial temperature of 150 °C is dropped into 1.2 kg of water at 25 °C. The final equilibrium temperature of the mixture is 30 °C. Assume no thermal energy is lost to the surroundings.
(a) Calculate the thermal energy lost by the copper block.
Working: _______________________________________________________________
Answer: _______________________ J [2]
(b) Calculate the thermal energy gained by the water.
Working: _______________________________________________________________
Answer: _______________________ J [2]
(c) Suggest a reason why the answers to (a) and (b) may not be exactly equal in a real experiment.
_____________________________________________________________________________ [1]
18. A vacuum flask is designed to keep hot liquids warm for as long as possible.
(a) Label the features A, B, and C on the diagram below and explain how each feature reduces thermal energy transfer.
┌──────────────────────┐
│ A: Plastic cap │
├──────────────────────┤
│ │
│ B: Vacuum layer │
│ │
├──────────────────────┤
│ C: Silvered walls │
└──────────────────────┘
Feature A (Plastic cap):
_____________________________________________________________________________ [1]
Feature B (Vacuum layer):
_____________________________________________________________________________ [1]
Feature C (Silvered walls):
_____________________________________________________________________________ [1]
19. A 1.5 kg sample of ice at 0 °C is heated until it completely melts into water at 0 °C. The specific latent heat of fusion of ice is 3.34 × 10⁵ J kg⁻¹.
(a) Calculate the thermal energy required to melt the ice completely.
Working: _______________________________________________________________
Answer: _______________________ J [2]
(b) Explain, in terms of molecular energy, why the temperature does not change during melting even though thermal energy is being supplied.
_____________________________________________________________________________ [2]
20. Two identical cans, one painted matt black and the other polished silver, are filled with equal amounts of hot water at 80 °C. They are left to cool in a room at 20 °C.
(a) Predict which can cools faster. Explain your answer.
_____________________________________________________________________________ [2]
(b) Sketch a graph of temperature (y-axis) against time (x-axis) for both cans on the same axes. Label your curves clearly.
Temperature / °C
|
|
|
|
|
|
|
|
|
|
+──────────────────────── Time / min
[2]
End of Quiz
Answers
Secondary 3 Physics Quiz - Thermal Physics
Answer Key
Section A: Multiple Choice Questions
1. B — J °C⁻¹ [1]
Heat capacity is the energy required to raise the temperature of a body by 1 °C. Its unit is joules per degree Celsius (J °C⁻¹). Option A is the unit for specific heat capacity.
2. A — 60 K [1]
A change in temperature in °C is numerically equal to the change in K. ΔT = 85 − 25 = 60 °C = 60 K.
3. B — overcome the intermolecular forces between molecules [1]
During boiling, energy is used to break intermolecular bonds (change of state), not to increase kinetic energy/temperature.
4. C — Radiation [1]
Radiation transfers energy via electromagnetic waves and does not require a medium. Conduction and convection require matter.
5. B — X has a higher temperature than Y [1]
Heat flows from a region of higher temperature to a region of lower temperature, regardless of mass, heat capacity, or volume.
6. B — raise the temperature of 1 kg of the substance by 1 °C [1]
Specific heat capacity is defined per unit mass (1 kg) per unit temperature change (1 °C or 1 K).
7. A — absorber and poor emitter [1]
A shiny silver surface is a poor absorber and a poor emitter of thermal radiation. It is a good reflector.
8. C — Solid [1]
In solids, particles are closely packed and transfer energy efficiently through vibrations. Conduction is most efficient in solids.
9. B — 10 °C [1]
Q = mcΔT → ΔT = Q / (mc) = 18 000 / (2 × 900) = 10 °C.
10. D — loses thermal energy but its temperature remains constant [1]
During condensation, the gas releases latent heat. The temperature remains constant during the change of state.
Section B: Short Answer and Structured Questions
11.
(a) Specific heat capacity is the amount of thermal energy required to raise the temperature of 1 kg of a substance by 1 °C (or 1 K). [2]
Marking: 1 mark for "1 kg", 1 mark for "by 1 °C / 1 K".
(b) Specific latent heat of fusion is the amount of thermal energy required to change 1 kg of a substance from solid to liquid at its melting point, without a change in temperature. [2]
Marking: 1 mark for "1 kg", 1 mark for "solid to liquid at constant temperature / without temperature change".
12. During melting, the thermal energy supplied is used to overcome the intermolecular forces holding the molecules in their fixed positions in the solid lattice. [1]
The energy increases the potential energy of the molecules, not their kinetic energy. [1]
Since temperature is a measure of the average kinetic energy of the molecules, and kinetic energy does not increase, the temperature remains constant. [1]
[3]
13.
| Boiling | Evaporation | |
|---|---|---|
| Difference 1 | Occurs at a fixed temperature (boiling point) | Occurs at any temperature |
| Difference 2 | Occurs throughout the bulk of the liquid | Occurs only at the surface of the liquid |
[2]
Marking: 1 mark per correct difference. Accept other valid differences, e.g., boiling requires a continuous heat source / evaporation is a slower process / boiling produces bubbles.
14.
(a) Q = mcΔT [1]
Q = 0.5 × 4 200 × (100 − 20)
Q = 0.5 × 4 200 × 80
Q = 168 000 J [1]
(b) P = E / t → t = E / P [1]
t = 168 000 / 500
t = 336 s [1]
15.
(a) Thermal energy travels from the heated end (near the Bunsen burner) towards the cooler end / from left to right along the rod. [1]
(b) The wax blobs near the heated end are closest to the heat source. [1] Thermal energy is transferred along the rod by conduction, so the nearest blobs receive thermal energy first and reach the melting point before the others. [1]
(c) Conduction [1]
16. The metal handle is in direct contact with the saucepan body, which is heated by the stove. [1] Thermal energy is transferred through the metal by conduction — the particles in the hot part of the saucepan vibrate more vigorously and pass on their kinetic energy to neighbouring particles along the handle. [1] Since metals are good conductors of thermal energy, the handle becomes hot. [1]
[2] — Award marks for: mention of conduction + explanation of particle vibration/energy transfer.
Section C: Longer Response and Application Questions
17.
(a) Thermal energy lost by copper:
Q = mcΔT [1]
Q = 0.8 × 385 × (150 − 30)
Q = 0.8 × 385 × 120
Q = 36 960 J (or 3.70 × 10⁴ J) [1]
(b) Thermal energy gained by water:
Q = mcΔT [1]
Q = 1.2 × 4 200 × (30 − 25)
Q = 1.2 × 4 200 × 5
Q = 25 200 J [1]
(c) Some thermal energy is lost to the surroundings (e.g., absorbed by the container, lost to the air). [1]
Accept: heat absorbed by the container / heat lost to the environment.
18.
Feature A (Plastic cap): Plastic is a poor conductor of heat (thermal insulator), so it reduces thermal energy loss by conduction through the top of the flask. [1]
Feature B (Vacuum layer): The vacuum (empty space between the walls) prevents thermal energy transfer by convection and conduction, as both require a medium and there are no particles in a vacuum. [1]
Feature C (Silvered walls): The silvered surfaces are poor emitters and good reflectors of thermal radiation, so they reflect thermal radiation back into the liquid and reduce energy loss by radiation. [1]
19.
(a) Q = m × l_f [1]
Q = 1.5 × 3.34 × 10⁵
Q = 5.01 × 10⁵ J (or 501 000 J) [1]
(b) During melting, the thermal energy supplied is used to break the intermolecular bonds that hold the water molecules in the solid ice lattice. [1] This energy increases the potential energy of the molecules, not their kinetic energy. Since temperature depends on the average kinetic energy of the molecules, the temperature remains constant during the change of state. [1]
[2]
20.
(a) The matt black can cools faster. [1] A matt black surface is a better emitter of thermal radiation compared to a polished silver surface, so it loses thermal energy to the surroundings at a faster rate. [1]
(b) Graph:
- Both curves start at 80 °C and decrease towards 20 °C (room temperature).
- The matt black can curve drops more steeply (cools faster).
- The polished silver can curve drops more gradually (cools slower).
- Both curves level off asymptotically towards 20 °C.
- Both curves must be clearly labelled. [2]
Marking: 1 mark for correct shape (decreasing, asymptotic to 20 °C), 1 mark for correct relative steepness and labelling.
End of Answer Key