IBPhysicsHLTopic QuestionsThe Particulate Nature of MatterThermodynamics

Syllabus Edition

First teaching 2023

First exams 2025

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Thermodynamics (HL IB Physics)

Topic Questions

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1
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A gas is kept in a closed container at room temperature. A lit Bunsen burner is then placed under this container.

Which row correctly describes the changes the gas undergoes?

 

work done on gas

change in internal energy
A positive positive
B zero zero
C positive zero
D zero positive

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2
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In which process is a gas doing the least amount of work?

pv-graph-options-1

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3
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An ideal gas in a simple engine undergoes the process shown in the pressure-volume graph below. 

The dashed lines represent isotherms and the line of the process can be accurately modelled with the following equation:

space p V to the power of 5 over 3 end exponent space equals space k

where k is a constant.

adiabatic-q3-ib-hl-physics

Which of the following statements are true?

  • No thermal energy is transferred from the gas to its surroundings.

  • The internal energy of the gas is constant.

  • Work is done on the gas.

  • The temperature of the surroundings increases.

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4
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A hypothetical car is running on a Carnot engine. 

Once the car has been driving for a while, the gas in the engine has a minimum temperature of 275 K. 

The engine has an efficiency of 0.75. What is the temperature range of the gas in the engine?

  • 92 K

  • 367 K

  • 825 K

  • 1100 K

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5
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An ideal gas undergoes an isobaric compression. It has an initial pressure of 150 kPa, an initial temperature of 16°C and an initial volume of 30 000 cm3. 

Initially, there were 12 moles of gas in the chamber. After the compression, the volume decreases by 0.005 m3.

What is the final pressure of the gas?

  • 48 kPa

  • 150 kPa

  • 240 kPa

  • 241 kPa

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1
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A electrical heater is has a current of 1.5 A passing through it and has a potential difference of 200 V across it. 

It heats a gas in a piston at a constant pressure of 30 kPa. After 15 s the volume of the gas has increases by 0.020 m3 and its internal energy has increased by 2000 J.

The electrical heater is 70% efficient. What proportion of the thermal energy output by the electric heater is transferred to the gas?

  • 0.44

  • 0.64

  • 0.70

  • 0.83

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2
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At 78.0°C, 12.0 g of liquid ammonia is converted to a gaseous state. The entropy change of this process is 0.0470 J K−1.

What is the latent heat of vaporisation of ammonia?

  • 16.5 J kg−1

  • 39.2 J kg−1

  • 306 J kg−1

  • 1370 J kg−1

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3
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In an adiabatic process, a gas in a piston does work.

The cylindrical chamber increases in length from 1.5 m to 290 cm.

Which expression, in terms of original pressure p, most closely represents the new pressure?

  • p over 5

  • p over 3

  • p over 2

  • 3 p

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4
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An idealised heat engine has an efficiency of η and is supplied with heat energy QH from an external hot reservoir.

The cycle is described as follows:

Stage 1: The gas undergoes isobaric compression at a pressure of p1. The volume decreases by z and the final temperature is T1.

Stage 2: The gas then undergoes isovolumetric heating. The final temperature is T2.

Stage 3: The gas undergoes isobaric expansion. The volume increases by z.

Stage 4: Finally, the gas undergoes isovolumetric cooling and returns to its state at the beginning of stage 1.

Which is the correct expression for z?

  • fraction numerator eta Q subscript H T subscript 1 over denominator p subscript 1 open parentheses T subscript 2 space minus space T subscript 1 close parentheses end fraction

  • fraction numerator p subscript 1 T subscript 1 open parentheses T subscript 2 space minus space T subscript 1 close parentheses over denominator eta Q subscript H end fraction

  • fraction numerator p subscript 1 open parentheses T subscript 1 space minus space T subscript 2 close parentheses over denominator T subscript 2 eta Q subscript H end fraction

  • fraction numerator Q subscript H T subscript 1 eta over denominator p subscript 1 open parentheses T subscript 1 space minus space T subscript 2 close parentheses end fraction

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5
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A researcher is studying phase changes of different materials.

They plot the following graph of heat supplied and entropy change for different masses of a material being vaporised. Their axes are incomplete. 

entropy-graph-ib-hl-physics

Using the following table, which material was being studied?

Material Melting point / °C Boiling point / °C
A. 375 560
B. 0 100
C. N/A −270
D. 0 230

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1
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An ideal gas in a simple engine begins in state X. It then undergoes a cyclic process with 4 stages.

Stage 1: The gas is isothermally compressed

Stage 2: The gas gains thermal energy without doing any work

Stage 3: The gas does work isobarically

Stage 4: The gas expands adiabatically

Which diagram correctly shows this cyclic process?

heat-engine-options-ib-hl-physics

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2
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In a box containing an unknown number of partitions, 15 particles are kept in a single section of the box behind one of the partitions.

When a small hole is opened in each of the partitions, the entropy increases by 1.12 × 10−22 J K−1. 

What is the final number of microstates of the system?

  • 8

  • 3300

  • 3400

  • 50 000

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3
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A simple heat engine contains 3 moles of an ideal gas. When the gas is cooled, the mean kinetic energy per particle drops by 3.11 × 10−21 J.

Additionally, 2 kJ of work is done on the gas. 

What is the thermal energy transferred from the gas to its surroundings?

  • 2000 J

  • 3620 J

  • 5620 J

  • 7620 J

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4
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A refrigerator in its surroundings does work and freezes a small amount of liquid water. Which row of the table is correct?

 

entropy of the water

temperature of the surroundings

entropy of the surroundings
A increases increases increases
B decreases increases increases
C stays the same decreases decreases
D decreases increases stays the same

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5
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The pressure-volume diagram below shows a cyclic process. The grey dashed lines represent isotherms.

novel-heat-engine-cycle-ib-hl-physics

Which option best describes the stages of the cyclic process, which begins at Z?

  • The gas expands isovolumetrically, loses pressure at constant internal energy, expands adiabatically. Work is then done on the gas in an isobaric manner.

  • The gas undergoes isovolumetric heating. It then does work adiabatically, before cooling adiabatically again but faster. Work is done on the gas in the final stage. 

  • The gas does no work while being heated, follows an isotherm and then expands adiabatically. Work is then done by the gas in the final stage.

  • The gas undergoes isovolumetric heating. It then does work isothermally, before cooling adiabatically. Work is done on the gas finally.

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