Thermal physicsAQA A-Level Physics: Topic test

20 questions, 54 marks

AQA A-Level Physics

Thermal physics topic test

Total 54 marks

Name

Class

Date

1
A 0.30 kg sample of solid paraffin wax is at its melting point. An immersion heater of power 60 W, with all of its energy transferred to the wax, takes 1000 s to melt the whole sample. The specific heat capacity of the liquid wax is 2.4 × 10³ J kg⁻¹ K⁻¹.
(a)
What is the specific latent heat of fusion of the wax?
[1 mark]
A1.8 × 10⁴ J kg⁻¹
B6.0 × 10⁴ J kg⁻¹
C2.0 × 10⁵ J kg⁻¹
D2.0 × 10² J kg⁻¹
(b)
Which row describes what happens to the particles of the wax as it melts?
[1 mark]
AMean kinetic energy increases and potential energy is unchanged.
BMean kinetic energy and potential energy both increase.
CMean kinetic energy and potential energy are both unchanged.
DMean kinetic energy is unchanged and potential energy increases.
(c)
After melting, the heater is left on for a further 200 s. Calculate the temperature rise of the liquid wax.
[2 marks]
Total for question 1: 4 marks
2
A car tyre has an internal volume of 0.030 m³ and contains air at 15 °C and a pressure of 2.2 × 10⁵ Pa. After a long motorway journey the air in the tyre is at 45 °C. Assume that the air behaves as an ideal gas and that the volume of the tyre does not change. Molar gas constant R = 8.31 J K⁻¹ mol⁻¹; Boltzmann constant k = 1.38 × 10⁻²³ J K⁻¹.
(a)
What is the pressure of the air in the tyre at the end of the journey?
[1 mark]
A2.4 × 10⁵ Pa
B6.6 × 10⁵ Pa
C2.2 × 10⁵ Pa
D2.0 × 10⁵ Pa
(b)
How many moles of air are in the tyre?
[1 mark]
A0.36 mol
B2.8 mol
C53 mol
D2.8 × 10³ mol
(c)
Calculate the number of air molecules in the tyre.
[2 marks]
Total for question 2: 4 marks
3
Nitrogen gas in a laboratory is at a temperature of 290 K. Treat the gas as ideal. The mass of one nitrogen molecule is 4.65 × 10⁻²⁶ kg. Boltzmann constant k = 1.38 × 10⁻²³ J K⁻¹.
(a)
Calculate the mean kinetic energy of a nitrogen molecule and the root mean square speed of the molecules.
[3 marks]
(b)
The nitrogen is sealed in a rigid container and its temperature is then doubled. Explain, using the molecular model of a gas, why the pressure increases.
[4 marks]
Total for question 3: 7 marks
4
A rigid sealed container of volume 4.0 × 10⁻³ m³ holds 0.20 mol of argon, which may be treated as an ideal gas, at an initial temperature of 300 K. A heater inside the container supplies 1.5 kJ of energy to the gas, and no energy escapes from the container. The molar mass of argon is 0.040 kg mol⁻¹. R = 8.31 J K⁻¹ mol⁻¹; k = 1.38 × 10⁻²³ J K⁻¹; Avogadro constant N_A = 6.02 × 10²³ mol⁻¹.
(a)
Explain why the internal energy of the argon is entirely kinetic energy, state why the internal energy of the gas increases by 1.5 kJ, and calculate the final temperature of the gas.
[6 marks]
(b)
Calculate the final pressure of the argon and the root mean square speed of its atoms at the final temperature. Explain, using the molecular model, why the pressure has increased.
[6 marks]
Total for question 4: 12 marks
5
A student investigates Charles's law using a fixed mass of dry air trapped in a flexible container whose pressure is kept constant. The volume of the air is 24.0 cm³ at 20 °C, and the air is then heated to 80 °C.
(a)
What is the volume of the air at 80 °C?
[1 mark]
A96 cm³
B31.0 cm³
C28.9 cm³
D19.9 cm³
(b)
The student plots volume against temperature in °C and extrapolates the line to zero volume. At which temperature does it reach zero volume?
[1 mark]
A−373 °C
B−100 °C
C+273 °C
D−273 °C
(c)
Another student says that the volume of the air will double if its temperature is doubled from 20 °C to 40 °C. Explain why this is wrong and calculate the actual factor by which the volume increases.
[2 marks]
Total for question 5: 4 marks
6
A copper block of mass 0.15 kg at 200 °C is dropped into 0.40 kg of water at 15 °C in a well-insulated container. The specific heat capacity of copper is 385 J kg⁻¹ K⁻¹ and that of water is 4180 J kg⁻¹ K⁻¹. Assume that no energy is transferred to the container or the surroundings, and that no water boils.
(a)
What is the final temperature of the block and the water?
[1 mark]
A21 °C
B31 °C
C108 °C
D194 °C
(b)
How much energy is transferred from the copper to the water?
[1 mark]
A1.2 × 10⁴ J
B1.0 × 10⁴ J
C58 J
D1.1 × 10⁵ J
(c)
Explain why the final temperature is much closer to the initial temperature of the water than to that of the copper.
[2 marks]
Total for question 6: 4 marks
7
A helium-filled weather balloon is released at ground level, where the helium has a volume of 8.0 m³, a pressure of 1.01 × 10⁵ Pa and a temperature of 288 K. The balloon rises to a height where the pressure of the helium is 2.5 × 10⁴ Pa and its temperature is 225 K. The helium behaves as an ideal gas and none escapes. R = 8.31 J K⁻¹ mol⁻¹; N_A = 6.02 × 10²³ mol⁻¹.
(a)
Calculate the volume of the helium at the higher altitude.
[3 marks]
(b)
Calculate the number of moles of helium in the balloon and the number of helium atoms.
[4 marks]
Total for question 7: 7 marks
8
A rigid cylinder of volume 0.060 m³ holds a mixture of 1.2 mol of hydrogen and 0.30 mol of oxygen at a temperature of 320 K. The molar masses are 2.0 × 10⁻³ kg mol⁻¹ for hydrogen and 32 × 10⁻³ kg mol⁻¹ for oxygen. Treat both gases as ideal and assume that they do not react. R = 8.31 J K⁻¹ mol⁻¹; k = 1.38 × 10⁻²³ J K⁻¹.
(a)
Compare the mean kinetic energies and the root mean square speeds of the hydrogen and oxygen molecules in the cylinder, supporting your answer with calculations.
[6 marks]
(b)
Calculate the pressure of the gas mixture and the total internal energy of the gas. The cylinder is then cooled to 160 K. State and explain what happens to the pressure and to the internal energy.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).