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Thermodynamics

© njctl.org AP Physics 2 Thermodynamics

PSI AP Physics 2 Name________________________________

Multiple-Choice

1. Which of the following is NOT true when two systems with unequal temperatures come

into contact with one another?

(A) Heat will flow until thermal equilibrium is reached

(B) No net heat flow occurs once thermal equilibrium is reached

(C) Entropy is reduced during the process

(D) The natural flow of heat will be from the warmer system to the colder system

2. When one end of a cold metal spoon is placed upright in a cup of hot coffee, the other end

eventually gets warmer. On the scale of the molecules of the spoon, which of the following is the

primary explanation of this phenomenon?

(A) Warmer molecules will rise to the top

(B) The hot molecules produce thermal radiation that is then absorbed by the colder

molecules.

(C) Higher-energy molecules hit lower-energy molecules, increasing their speed and thus

their temperature.

(D) Hotter areas have more molecules, which will flow upwards from areas of high

concentration to low concentration.

3. It is 20∘𝐶 outside in Josh’s backyard. If her crabapple tree only blooms when the temperature

is about 25∘𝐶, what will the temperature need to be in Fahrenheit before they bloom?

(A) 71∘𝐹

(B) 77∘𝐹

(C) 85∘𝐹

(D) 25∘𝐹

4. Rose doesn’t feel well, but her mom will only let her stay home from school if she has a fever.

She knows that she needs to have a temperature that is at least 99. 5∘𝐹 before she is allowed to

stay home, but her thermometer works in Celsius instead of Fahrenheit. What temperature does

the thermometer need to be?

(A) 99. 5∘𝐶

(B) 27. 5∘𝐶

(C) 37. 5∘𝐶

(D) 38. 5∘𝐶

5. If systems 2 and 3 are both at thermal equilibrium with system 1, which of the following must be

true?

(A) Systems 2 and 3 are in thermal equilibrium with each other

(B) System 2 has a higher temperature than system 3

(C) System 3 has a higher temperature than system 2

(D) Systems 2 and 3 are not in thermal equilibrium with each other

Thermodynamics


6. Assuming that the coefficient of linear expansion of a metal bar is is the same from 0°C to 50°C,

which of the following temperature changes will produce the largest percent increase in the

length of a metal bar? (select 2 answers).

(A) An increase in temperature from 10° C to 14° C

(B) An increase in temperature from 30° C to 31° C

(C) An increase in temperature from 293 K to 297 K

(D) A decrease in temperature from 48° C to 40° C

7. A metal cup is left outdoors in the hot sun. As the cup’s temperature increases, which of the

following statements about the inner and outer circumferences of the cup is true?

(A) The outer circumference will not change, but the inner circumference will decrease.

(B) The outer circumference will increase, but the inner circumference will not change.

(C) The outer circumference will increase, but the inner circumference will decrease.

(D) Both the outer and the inner circumferences will increase.

8. A bimetal plate consists of two materials of different coefficients of

thermal expansion. The coefficient of thermal expansion of the top

part of the plate is less than the bottom part. If the temperature of

the entire plate increases, what happens to the plate?

(A) Expands

(B) Contracts

(C) Stays the same

(D) Bends up

9. A flat metal ring as shown increases in temperature over time. How will

its shape change? (select 2 answers)

(A) The inner radius will decrease

(B) The outer radius will increase

(C) The inner radius will increase

(D) The outer radius will decrease

10. At midnight, the temperature is 10 °C. At noon the next day, the temperature is 20°C. If a glass

building was 413m tall at midnight, how many meters did it grow during the day? (The

coefficient of linear thermal expansion for glass is approximately 8.5𝑥10−6 (∘𝐶)−1)

(A) 413 m

(B) 0.7 m

(C) 0.0

(D) 0.011 m

Thermodynamics


11. A solid copper ball with a mass of 50g and a temperature of 30 degrees Celsius is placed on a

sheet of ice at 0 °C, which then melts. If 50g of water at the same temperature were poured on

the ice, would it melt the same amount of ice as the copper ball?

(A) The water would melt more ice

(B) The water would melt less ice

(C) The water would melt the same amount of ice

(D) Neither would melt any ice

12. Two metal bars are kept at the same temperature and are aligned with their nearer ends

separated by a distance of 0.1m. Their far ends are clamped in place. One bar is made out of

steel (𝛼 = 10−5 (°𝐶)−1). The other is made out of iron (𝛼 = 1.2 × 10−5(°𝐶)−1). If the steel bar is

initially 4 m long and the iron bar is initially 5 m long, how much must the temperature of the

bars be changed to get them to touch?

(A) 10∘𝐶

(B) 100∘𝐶

(C) 1000∘𝐶

(D) 10000∘𝐶

13. The specific heat of a liquid is 1000 J/(kg•K). How much heat is needed to raise the temperature

of 2 kg of this liquid from 10∘𝐶 to 20∘𝐶?

(A) 2,000 J

(B) 10,000 J

(C) 20,000 J

(D) 40,000 J

14. Approximately how much heat must be removed from 0.5 kg of 50 °C water to freeze it into 0 °C

ice? [for water Lf = 334,000 J/kg and c = 4200 J/(kg•K) ]

(A) 105 J

(B) 105,000 J

(C) 167,000 J

(D) 272,000 J

15. Which of the following is true about melting process?

(A) The energy is required to increase the average kinetic energy of molecules

(B) The energy is required to decrease the average kinetic energy of molecules

(C) The energy is required to increase the potential energy between the molecules

(D) No energy is required for this process it happens spontaneously

Thermodynamics


16. A metal rod is placed so that it connects a heat source at 100°C and a heat sink at 10°C.

During time t, an amount of heat Q is transferred from the source to the sink. if the metal rod is

replaced by another made of the same material but of three times the length, how much heat

will be transferred during the same amount of time t?

(A) 1/9 Q

(B) 1/3 Q

(C) Q

(D) 3 Q

17. When we touch a piece of metal and a piece of wood that are placed in the same room, the

piece of metal feels much colder than the piece of wood. This happens because of the

difference in:

(A) Specific heat

(B) Temperature

(C) Thermal conductivity

(D) Latent heat

18. Given their coefficients of thermal conductivity, which of the following materials would best

insulate a building?

(A) Diamond (k= 2000 W/m•K)

(B) Glass (k= 1 W/m•K)

(C) Asbestos (k= 0.09 W/m•K)

(D) Air (k=0.026 W/m•K)

19. The state of an ideal gas was changed three times at three different

temperatures. The diagram represents three different isothermal curves.

Which of the following is true about the temperature of the gas?

(A) T1 < T2 < T3

(B) T1 > T2 > T3

(C) T1 > T2 < T3

(D) T1 > T2 = T3

20. The state of an ideal gas was changed three times in a way that the pressure

stays the same. The graph represents three isobaric lines. Which of the

following is true about the pressure of the gas?

(A) P1 > P2 > P3

(B) P1 > P2 < P3

(C) P1 < P2 < P3

(D) P1 = P2 > P3

Thermodynamics


21. Kinetic Theory is based on an ideal gas model. The following statements about the ideal gas are

true EXCEPT:

(A) All molecules move with the same speed

(B) The average molecular kinetic energy is directly proportional to the absolute temperature

(C) All molecules make elastic collisions with each other and the walls of the container

(D) The attractive force between the molecules can be ignored

22. Helium gas is sealed in a container. The container is heated, causing the temperature to

increase at a constant rate. Which of the following statements is NOT true?

(A) The pressure of the gas increases at a constant rate

(B) Temperature of the gas increases at a constant rate

(C) The average kinetic energy of the gas particles increases at a constant rate

(D) The average speed of the gas particles increases at a constant rate

23. A cylindrical container is sealed by a circular lid. The pressure in the room surrounding the

container is 1.0 × 105 N/m2. The pressure inside the container is 0.3 × 105 N/m2. The lid has

radius 0.10 m and weight 100 N. What is the minimum force required to lift the lid off of the

container?

(A) 3.15 × 103 N

(B) 2.20 × 103 N

(C) 2.30 × 103 N

(D) 1.04 × 103 N

24. A gas with volume V, pressure P, and temperature T is trapped inside a cylindrical container

with a moveable piston. If the temperature of a trapped gas is quadrupled while the volume is

doubled, what will be the new pressure?

(A) P

(B) 1.5P

(C) 2P

(D) 3P

25. A cylindrical container of volume V holds 3 moles of Neon gas with pressure P and temperature

T. If the gas is heated to a temperature of 2T and volume is kept constant, how many moles of

gas are there in the container?

(A) 3 moles

(B) 1.5 moles

(C) 1 mole

(D) 0 moles

Thermodynamics


26. A box contains a volume V of air with a pressure P and temperature T. If the box is never

opened and no air can escape. If the temperature in the room is increased to 2T, what will be

the new pressure in the box?

(A) ½ P

(B) P

(C) 2 P

(D) 4 P

27. A sample of ideal gas has an internal energy U and is then compressed to one-half of its original

volume while the temperature stays the same. What is the new internal energy of the ideal gas

in terms of U?

(A) U

(B) U/2

(C) U/4

(D) 2U

28. An ideal gas with an internal energy U initially at 0 ̊C is heated to 273 ̊C. What is the new

internal energy in terms of U?

(A) U

(B) 1/2U

(C) 1/4U

(D) 2U

29. Three containers are filled with 1 kg of each: water, ice, and water vapor at the same

temperature T = 0°C. Which of the following is true about the internal energy of the substances?

(A) U water > U ice > U vapor

(B) U water = U ice = U vapor

(C) U water < U ice < U vapor

(D) U ice < U water < U vapor

30. An ideal gas is initially in state A, as shown in the PV diagram (above). The gas undergoes a

transition from state A by the three different processes shown, where process III is isothermal.

Which of the following processes shows positive work being done on the gas?

(A) I only

(B) III only

(C) I and II only

(D) I, II, and III

Thermodynamics


31. An ideal gas is initially in state A, as shown in the PV diagram (above). The gas undergoes a transition from state A by the three different processes shown, where process III is isothermal. In which process is energy added to the gas?

(A) I only (B) III only (C) I and II only (D) II and III only

32. A sample of an ideal gas can be taken from state A to state B

through one of two processes, as shown in the graph of pressure P versus volume V (right). Which of the following will be the same for both processes?

(A) The average kinetic energy of the gas (B) The temperature of the gas at the end of the process (C) The thermal energy transferred to the gas by heating (D) The work done on the gas

33. Identical samples of gas initially have pressure 3P and volume 2V. The final temperature is equal to the initial temperature for which of the processes? (select 2 answers)

(A) A (B) B (C) C (D) D

34. Referring to the P-V diagram (right), how much work is done by the gas as it cycles once along

the path A → B → C → A?

(A) PV

(B) ½ PV

(C) 2 PV

(D) 4 PV

Thermodynamics


Use the diagram below right to answer questions 26 and 27

35. Which of the following lines on the graph above shows an adiabatic

process? (Select two answers)

(A) a-b (B) b-c (C) c-d (D) d-a

36. Which of the following lines on the graph above shows an isothermal

process? (Select two answers)

(A) a-b

(B) b-c

(C) c-d

(D) d-a

37. The state of an ideal gas is changed isothermally from position 1 to

position 2 is shown right. What is the change in the internal energy of the

gas during this process?

(A) ΔU = W

(B) ΔU = Q

(C) ΔU > 0

(D) ΔU = 0

38. An ideal gas is taken from state 1 to state 2 and then to state 3. If the

process 1-2 is adiabatic and 2-3 is isothermal, what is a true statement

about the change in temperature and heat transferred during 1-2?

(A) ΔT > 0, Q > 0

(B) ΔT < 0, Q = 0

(C) ΔT = 0, Q = 0

(D) ΔT = 0, Q < 0

39. Why does the isothermal curve look the way it does?

(A) PV= nRT, so the PV graph is comparable to the graph of 𝑦 = 𝑥

(B) PV= nRT, so the PV graph is comparable to the graph of 𝑦 = 𝑥2

(C) PV= nRT, so the PV graph is comparable to the graph of 𝑦 = 1/𝑥

(D) PV= nRT, so the PV graph is comparable to the graph of 𝑦 = 𝑥3

40. Which of the following is a characteristic of an adiabatic process?

(A) ΔU = 0

(B) W = 0

(C) Q = 0

(D) ΔV = 0

Thermodynamics


41. A container is filled with Helium gas to a pressure P at a temperature T. Oxygen, which has

atoms that are 4 times more massive than those of helium, is then added to the container until

the new pressure in the container is 2P at the same temperature T. The ratio of the average

speed of the helium atoms to the average speed of the Oxygen atoms is

(A) 4 to 1

(B) 2 to 1

(C) √2 to 1

(D) 1 to 1

42. A container is filled with Helium gas to a pressure P at a temperature T. Oxygen, which has atoms that are 4 times more massive than those of helium, is then added to the container until the new pressure in the container is 2P at the same temperature T. The ratio of the number of helium atoms to oxygen atoms in the container is

(A) 5 to 1 (B) 6 to 1 (C) 16 to 1 (D) 1 to 1

43. A sealed container of air is kept at a constant temperature. What will happen to the

speed/average kinetic energy of the molecules of air in the container as time passes?

(A) The molecules will obey the second law of thermodynamics. Eventually, there will be no

deviations in the speed of kinetic energy of the air molecules whatsoever.

(B) Some molecules will speed up and others will slow down, but the average speed and

kinetic energy will be constant.

(C) The molecules will slow down, decreasing their average kinetic energy.

(D) There will be no change

44. Two boxes of equal volume each contain the same quantity of an ideal gas. The first box is

much warmer than the second box. Which of the following statements MUST be true? (select 2

answers)

(A) The pressure in the first box is greater than the pressure in the second box

(B) There are more molecules in the first box than in the second box

(C) The boxes contain different types of gasses

(D) The molecules in the first box have a higher average kinetic energy than those in the

second box

45. During a thermodynamic process, 2,000 J of heat are removed from a gas while 600 J of work is

done by the gas. What is the change in internal energy of the gas?

(A) +2,600 J

(B) 0

(C) -1,400 J

(D) -2,600 J

Thermodynamics


46. The internal energy of a sample of confined helium gas is increased by 300 J. If the net amount

of work done on the sample by its surroundings was 240 J, how much heat was transferred

between the gas and its environment?

(A) 60 J absorbed

(B) 540 J absorbed

(C) 60 J dissipated

(D) 540 J dissipated

47. Ice is placed in an empty container in a room where the air temperature is 20°C and allow to melt. While the ice is melting the temperature of the water is…

(A) less than 0°C (B) 0°C (C) room temperature (D) greater than 0°C but less than room temperature

48. A gas undergoes an expansion in which 300 J of energy is added to the gas by heating. The internal energy of the gas changes from 600 J to 700 J. The work done by the gas is:

(A) 1,300 J (B) 900 J (C) 200 J (D) 100 J

49. Convection can occur in which of the following substances? (Select two answers)

(A) Solids

(B) Liquids

(C) Bose-Einstein Condensate

(D) Gasses

50. If the absolute temperature of a radiating object is doubled, by what factor does the rate of

energy emission change?

(A) 2

(B) 4

(C) 16

(D) 32

51. The product of pressure and volume is expressed most commonly in which of the following

units:

(A) Joules

(B) Pascal∙meters2

(C) Farads

(D) Pascals

Thermodynamics


52. A gas trapped in a container with a movable piston undergoes an adiabatic process. During this

process, the gas does about 1025 joules of work. Which of the following statements are true?

(select 2 answers)

(A) The internal energy of the system increases by 1025 J

(B) The temperature of the gas increases

(C) The temperature of the gas decreases

(D) The heat transferred in or out of the system is zero

53. At higher altitudes, the air is colder. Why does this happen?

(A) There are fewer air molecules at higher altitudes, so are less collisions between

molecules and the air loses energy quickly.

(B) As a quantity of air moves to a higher altitude, it experiences a decrease in pressure.

This causes the air to expand. Since no heat is being added, the internal energy of the

air drops, and therefore its temperature drops.

(C) There are fewer people living in higher altitudes, at much of the warmth of our planet

comes from human emissions like body heat and greenhouse gasses that are heavily

concentrated in more populated areas.

(D) It is not colder in higher altitudes.

54. Which statement must be true regarding two systems of unequal temperature that come in

contact with one another?

(A) The final temperature will be the average of the two systems’ temperatures

(B) The final temperature will be greater than that of the warmer system

(C) There will be a decrease in total energy

(D) The total amount of thermal energy will be constant

55. An engine has an efficiency of 20% and produces 2000 J of mechanical work during one cycle. How much energy is transferred out of the engine by heating the environment during one cycle?

(A) 100 J

(B) 2000 J

(C) 8000 J

(D) 10000 J

Questions 56-58: A Carnot engine takes 2000 J of heat from a reservoir at 200∘𝐶, does some work, and

releases some heat into a second reservoir at 20°𝐶.

56. What is the efficiency of the engine?

(A) 4%

(B) 10%

(C) 38%

(D) 90%

Thermodynamics


57. How much work is done by the engine?

(A) 80 J

(B) 200 J

(C) 1800 J

(D) 760 J

58. How much heat is discarded by the engine?

(A) 1340 J

(B) 1920 J

(C) 1800 J

(D) 200 J

Thermodynamics


Answer Key

1. c 2. c 3. b 4. c 5. a 6. a,c

7. d 8. d 9. b,c 10. c 11. b 12. c

13. c 14. d 15. c 16. b 17. c 18. d

19. a 20. c 21. a 22. d 23. c 24. c

25. a 26. c 27. a 28. d 29. d 30. a

31. b 32. b 33. a,c 34. a 35. a,c 36. b,d

37. d 38. b 39. c 40. c 41. b 42. d

43. b 44. a,d 45. d 46. b 47. b 48. c

49. b,d 50. c 51. a 52. c,d 53. b 54. d

55. c 56. c 57. d 58. a

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