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Thermodynamics (DP IB Physics: HL): Exam Questions

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Thermodynamics

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11 mark

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

    Choose your answer

    21 mark

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

    pv-graph-options-1

      Choose your answer

      31 mark

      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.

      Choose your answer

      4
      Sme Calculator      1 mark

      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

      Choose your answer

      5
      Sme Calculator      1 mark

      An ideal gas has an initial pressure of 150 kPa, an initial temperature of 27°C, and an initial volume of 0.2 m3. During an isobaric compression, the volume of the gas decreases by 0.005 m3.

      What is the final pressure of the gas?

      • 50 kPa

      • 150 kPa

      • 240 kPa

      • 480 kPa

      Choose your answer

      11 mark

      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

        Choose your answer

        2
        Sme Calculator        1 mark

        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?

        • 8.0 × 100

        • 1.2 × 102

        • 3.3 × 103

        • 5.0 × 104

        Choose your answer

        3
        Sme Calculator        1 mark

        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

        Choose your answer

        41 mark

        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

          Choose your answer

          51 mark

          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.

          Choose your answer

          1
          Sme Calculator          1 mark

          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

          Choose your answer

          2
          Sme Calculator          1 mark

          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

          Choose your answer

          3
          Sme Calculator          1 mark

          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

          Choose your answer

          41 mark

          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

          Choose your answer

          5
          Sme Calculator          1 mark

          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

            Choose your answer