Ch18 Exam Questions Temperature, Heat, And The First Law Of

Chapter: Chapter 18

Learning Objectives

LO 18.1.0 Solve problems related to temperature.

LO 18.1.1 Identify the lowest temperature as 0 on the Kelvin scale (absolute zero).

LO 18.1.2 Explain the zeroth law of thermodynamics.

LO 18.1.3 Explain the conditions for the triple-point temperature.

LO 18.1.4 Explain the conditions for measuring a temperature with a constant-volume gas thermometer.

LO 18.1.5 For a constant-volume gas thermometer, relate the pressure and temperature of the gas in some given state to the pressure and temperature at the triple point.

LO 18.2.0 Solve problems related to the Celsius and Fahrenheit scales.

LO 18.2.1 Convert a temperature between any two (linear) temperature scales, including the Celsius, Fahrenheit, and Kelvin scales.

LO 18.2.2 Identify that a change of one degree is the same on the Celsius and Kelvin scales.

LO 18.3.0 Solve problems related to thermal expansion.

LO 18.3.1 For one-dimensional thermal expansion, apply the relationship between the temperature change ΔT, the length change ΔL, the initial length L, and the coefficient of linear expansion α.

LO 18.3.2 For two-dimensional thermal expansion, use one-dimensional thermal expansion to find the change in area.

LO 18.3.3 For three-dimensional thermal expansion, apply the relationship between the temperature change ΔT, the volume change ΔV, the initial volume V, and the coefficient of volume expansion β.

LO 18.4.0 Solve problems related to absorption of heat.

LO 18.4.1 Identify that thermal energy is associated with the random motions of the microscopic bodies in an object.

LO 18.4.2 Identify that heat Q is the amount of transferred energy (either to or from an object’s thermal energy) due to a temperature difference between the object and its environment.

LO 18.4.3 Convert energy units between various measurement systems.

LO 18.4.4 Convert between mechanical or electrical energy and thermal energy.

LO 18.4.5 For a temperature change ΔT of a substance, relate the change to the heat transfer Q and the substance’s heat capacity C.

LO 18.4.6 For a temperature change ΔT of a substance, relate the change to the heat transfer Q and the substance’s specific heat c and mass m.

LO 18.4.7 Identify the three phases of matter.

LO 18.4.8 For a phase change of a substance, relate the heat transfer Q, the heat of transformation L, and the amount of mass m transformed.

LO 18.4.9 Identify that if a heat transfer Q takes a substance across a phase-change temperature, the transfer must be calculated in steps: (a) a temperature change to reach the phase-change temperature, (b) the phase change, and then (c) any temperature change that moves the substance away from the phase-change temperature.

LO 18.5.0 Solve problems related to the first law of thermodynamics.

LO 18.5.1 If an enclosed gas expands or contracts, calculate the work W done by the gas by integrating the gas pressure with respect to the volume of the enclosure.

LO 18.5.2 Identify the algebraic sign of work W associated with expansion and contraction of a gas.

LO 18.5.3 Given a p-V graph of pressure versus volume for a gas, identify the starting point (the initial state) and the final point (the final state) and calculate the work by using graphical integration.

LO 18.5.4 On a p-V graph of pressure versus volume for a gas, identify the algebraic sign of the work associated with a right-going process and a left-going process.

LO 18.5.5 Apply the first law of thermodynamics to relate the change in the internal energy ΔE_int of a gas, the energy Q transferred as heat to or from the gas, and the work W done on or by the gas.

LO 18.5.6 Identify the algebraic sign of a heat transfer Q that is associated with a transfer to a gas and a transfer from the gas.

LO 18.5.7 Identify that the internal energy ΔE_int of a gas tends to increase if the heat transfer is to the gas, and it tends to decrease if the gas does work on its environment.

LO 18.5.8 Identify that in an adiabatic process with a gas, there is no heat transfer Q with the environment.

LO 18.5.9 Identify that in a constant-volume process with a gas, there is no work W done by the gas.

LO 18.5.10 Identify that in a cyclical process with a gas, there is no net change in the internal energy ΔE_int.

LO 18.5.11 Identify that in a free expansion with a gas, the heat transfer Q, work done W, and change in internal energy ΔE_int are each zero.

LO 18.6.0 Solve problems related to heat transfer mechanisms.

LO 18.6.1 For thermal conduction through a layer, apply the relationship between the energy-transfer rate P_cond and the layer’s area A, thermal conductivity k, thickness L, and temperature difference ΔT (between its two sides).

LO 18.6.2 For a composite slab (two or more layers) that has reached the steady state in which temperatures are no longer changing, identify that (by the conservation of energy) the rates of thermal conduction P_cond through the layers must be equal.

LO 18.6.3 For thermal conduction through a layer, apply the relationship between thermal resistance R, thickness L, and thermal conductivity k.

LO 18.6.4 Identify that thermal energy can be transferred by convection, in which a warmer fluid (gas or liquid) tends to rise in a cooler fluid.

LO 18.6.5 In the emission of thermal radiation by an object, apply the relationship between the energy-transfer rate P_rad and the object’s surface area A, emissivity ε, and surface temperature T (in kelvins).

LO 18.6.6 In the absorption of thermal radiation by an object, apply the relationship between the energy-transfer rate P_abs and the object’s surface area A and emissivity ε, and the environmental temperature T (in kelvins).

LO 18.6.7 Calculate the net energy-transfer rate P_net of an object emitting radiation to its environment and absorbing radiation from that environment.

Multiple Choice

1. The international standard thermometer is kept:

A) near Washington, D.C.

B) near Paris, France

C) near the north pole

D) near Rome, Italy

E) nowhere (there is none)

Difficulty: E

Section: 18-1

Learning Objective 18.1.0

2. In constructing a thermometer it is NECESSARY to use a substance that:

A) expands with rising temperature

B) expands linearly with rising temperature

C) will not freeze

D) will not boil

E) undergoes some change when heated or cooled

Difficulty: E

Section: 18-1

Learning Objective 18.1.0

3. What is the limiting low temperature of a physical object?

A) there is no limiting low temperature

B) 0 K

C) 0° C

D) 0° F

E) –100° C

Difficulty: E

Section: 18-1

Learning Objective 18.1.1

4. If two objects are in thermal equilibrium with each other

A) they cannot be moving

B) they cannot be undergoing an elastic collision

C) they cannot have different pressures

D) they cannot be at different temperatures

E) they cannot be falling in the Earth's gravitational field

Difficulty: E

Section: 18-1

Learning Objective 18.1.2

5. When two gases separated by a diathermal wall are in thermal equilibrium with each other:

A) only their pressure must be the same

B) only their volumes must be the same

C) they must have the same number of particles

D) they must have the same pressure and the same volume

E) only their temperatures must be the same

Difficulty: E

Section: 18-1

Learning Objective 18.1.2

6. A balloon is filled with cold air and placed in a warm room. It is NOT in thermal equilibrium with the air of the room until

A) it rises to the ceiling

B) it sinks to the floor

C) it stops expanding

D) it starts to contract

E) none of the above

Difficulty: E

Section: 18-1

Learning Objective 18.1.2

7. Suppose object C is in thermal equilibrium with object A and with object B. The zeroth law of thermodynamics states:

A) that C will always be in thermal equilibrium with both A and B

B) that C must transfer energy to both A and B

C) that A is in thermal equilibrium with B

D) that A cannot be in thermal equilibrium with B

E) nothing about the relationship between A and B

Difficulty: E

Section: 18-1

Learning Objective 18.1.2

8. The zeroth law of thermodynamics allows us to define

A) work

B) pressure

C) temperature

D) thermal equilibrium

E) internal energy

Difficulty: E

Section: 18-1

Learning Objective 18.1.2

9. If the zeroth law of thermodynamics were not valid, which of the following could not be considered a property of an object?

A) Pressure

B) Center of mass energy

C) Internal energy

D) Momentum

E) Temperature

Difficulty: E

Section: 18-1

Learning Objective 18.1.2

10. The "triple point" of a substance is that point for which the temperature and pressure are such that:

A) only solid and liquid are in equilibrium

B) only liquid and vapor are in equilibrium

C) only solid and vapor are in equilibrium

D) solid, liquid and vapor are all in equilibrium

E) the temperature, pressure and density are all numerically equal

Difficulty: E

Section: 18-1

Learning Objective 18.1.3

11. Constant-volume gas thermometers using different gases all indicate nearly the same temperature when in contact with the same object if:

A) the volumes are all extremely large

B) the volumes are all the same

C) the pressures are all extremely large

D) the pressures are the same

E) the particle concentrations are all extremely small

Difficulty: E

Section: 18-1

Learning Objective 18.1.4

12. A constant-volume gas thermometer is used to measure the temperature of an object. When the thermometer is in contact with water at its triple point (273 K) the pressure in the thermometer is 8.50  10⁴ Pa. When it is in contact with the object the pressure is 9.65  10⁴ Pa. The temperature of the object is:

A) 41.0 K

B) 114 K

C) 241 K

D) 310 K

E) 314 K

Difficulty: E

Section: 18-1

Learning Objective 18.1.5

13. When a certain constant volume gas thermometer is in thermal contact with water at its triple point (273.16 K) the pressure is 6.30  10⁴ Pa. For this thermometer a kelvin corresponds to a change in pressure of about:

A) 4.34  10² Pa

B) 2.31  10² Pa

C) 1.72  10³ Pa

D) 2.31  10³ Pa

E) 1.72  10⁷ Pa

Difficulty: M

Section: 18-1

Learning Objective 18.1.5

14. The diagram shows four thermometers, labeled W, X, Y, and Z. The freezing and boiling points of water are indicated. Rank the thermometers according to the size of a degree on their scales, smallest to largest.

A) W, X, Y, Z

B) Y, W, X, Z

C) Z, Y, W, X

D) Z, X, W, Y

E) W, Y, Z, X

Difficulty: E

Section: 18-2

Learning Objective 18.2.0

15. There is a temperature at which the reading on the Kelvin scale is numerically:

A) equal to that on the Celsius scale

B) lower than that on the Celsius scale

C) equal to that on the Fahrenheit scale

D) less than zero

E) none of the above

Difficulty: E

Section: 18-2

Learning Objective 18.2.1

16. Fahrenheit and Kelvin scales agree numerically at a reading of:

A) –40°

B) 0°

C) 273°

D) 301°

E) 574°

Difficulty: M

Section: 18-2

Learning Objective 18.2.1

17. Which one of the following statements is true?

A) temperatures differing by 25 on the Fahrenheit scale must differ by 45 on the Celsius scale

B) 40 K corresponds to –40C

C) temperatures which differ by 10 on the Celsius scale must differ by 18 on the Fahrenheit scale

D) water at 90C is warmer than water at 202F

E) 0F corresponds to –32C

Difficulty: M

Section: 18-2

Learning Objective 18.2.1

18. A Kelvin thermometer and a Fahrenheit thermometer both give the same reading for a certain sample. The corresponding Celsius temperature is:

A) 574C

B) 232C

C) 301C

D) 614C

E) 276C

Difficulty: M

Section: 18-2

Learning Objective 18.2.1

19. Room temperature is about 20 degrees on the:

A) Kelvin scale

B) Celsius scale

C) Fahrenheit scale

D) absolute scale

E) C major scale

Difficulty: E

Section: 18-2

Learning Objective 18.2.1

20. A thermometer indicates 98.6C. It may be:

A) outdoors on a cold day

B) in a comfortable room

C) in a cup of hot tea

D) in a normal person's mouth

E) in liquid air

Difficulty: E

Section: 18-2

Learning Objective 18.2.1

21. The air temperature on a summer day might be about:

A) 0C

B) 10C

C) 25C

D) 80C

E) 125C

Difficulty: E

Section: 18-2

Learning Objective 18.2.1

22. One degree is the same on the following temperature scales:

A) Fahrenheit and Celsius

B) Fahrenheit and Kelvin

C) Celsius and Kelvin

D) Fahrenheit and Absolute

E) none of the above

Difficulty: E

Section: 18-2

Learning Objective 18.2.2

23. It is more difficult to measure the coefficient of volume expansion of a liquid than that of a solid because:

A) no relation exists between linear and volume expansion coefficients

B) a liquid tends to evaporate

C) a liquid expands too much when heated

D) a liquid expands too little when heated

E) the containing vessel also expands

Difficulty: E

Section: 18-3

Learning Objective 18.3.0

24. Possible units for the coefficient of volume expansion are:

A) mm/C

B) mm³/C

C) (C)³

D) 1/(C)³

E) 1/C

Difficulty: E

Section: 18-3

Learning Objective 18.3.0

25. The two metallic strips that constitute some thermostats must differ in:

A) length

B) thickness

C) mass

D) rate at which they conduct heat

E) coefficient of linear expansion

Difficulty: E

Section: 18-3

Learning Objective 18.3.1

26. Thin strips of iron and zinc are riveted together to form a bimetallic strip which bends when heated. The iron is on the inside of the bend because:

A) it has a higher coefficient of linear expansion

B) it has a lower coefficient of linear expansion

C) it has a higher specific heat

D) it has a lower specific heat

E) it conducts heat better

Difficulty: E

Section: 18-3

Learning Objective 18.3.1

27. A surveyor's 30-m steel tape is correct at 68F. On a hot day the tape has expanded to 30.02 m. On that day, the tape indicates a distance of 15.52 m between two points. The true distance between these points is:

A) 15.50 m

B) 15.51 m

C) 15.52 m

D) 15.53 m

E) 15.54 m

Difficulty: M

Section: 18-3

Learning Objective 18.3.1

28. The Stanford linear accelerator contains hundreds of brass disks tightly fitted into a steel tube (see figure). The coefficient of linear expansion of the brass is 2.00  10^–5 per C. The system was assembled by cooling the disks in dry ice (–57C) to enable them to just slide into the close-fitting tube. If the diameter of a disk is 80.00 mm at 43C, what is its diameter in the dry ice?

A) 78.400 mm

B) 79.998 mm

C) 80.160 mm

D) 79.840 mm

E) none of these

Difficulty: M

Section: 18-3

Learning Objective 18.3.1

29. When the temperature of a copper penny is increased by 100 C, its diameter increases by 0.17%. The area of one of its faces increases by:

A) 0.17%

B) 0.34%

C) 0.51%

D) 0.13%

E) 0.27%

Difficulty: M

Section: 18-3

Learning Objective 18.3.2

30. The figure shows a rectangular brass plate at 0C in which there is cut a rectangular hole of dimensions indicated. If the temperature of the plate is raised to 150C:

A) x will increase and y will decrease

B) both x and y will decrease

C) x will decrease and y will increase

D) both x and y will increase

E) the changes in x and y depend on the dimension z

Difficulty: E

Section: 18-3

Learning Objective 18.3.2

31. An annular ring of aluminum is cut from an aluminum sheet as shown. When this ring is heated:

A) the aluminum expands outward and the hole remains the same in size

B) the hole decreases in diameter

C) the area of the hole expands the same percent as any area of the aluminum

D) the area of the hole expands a greater percent than any area of the aluminum

E) linear expansion forces the shape of the hole to be slightly elliptical

Difficulty: E

Section: 18-3

Learning Objective 18.3.2

32. The diagram shows four rectangular plates and their dimensions. All are made of the same material. The temperature now increases. Of these plates:

A) the vertical dimension of plate 1 increases the most and the area of plate 1 increases the most

B) the vertical dimension of plate 2 increases the most and the area of plate 4 increases the most

C) the vertical dimension of plate 3 increases the most and the area of plate 1 increases the most

D) the vertical dimension of plate 4 increases the most and the area of plate 3 increases the most

E) the vertical dimension of plate 4 increases the most and the area of plate 4 increases the most

Difficulty: E

Section: 18-3

Learning Objective 18.3.2

33. The mercury column in an ordinary medical thermometer doubles in length when its temperature changes from 95F to 105F. Choose the correct statement:

A) the coefficient of volume expansion of mercury is 0.10 per F

B) the coefficient of volume expansion of mercury is 0.30 per F

C) the coefficient of volume expansion of mercury is (0.10/3) per F

D) the vacuum above the column helps to "pull up" the mercury this large amount

E) none of the above is true

Difficulty: H

Section: 18-3

Learning Objective 18.3.3

34. The coefficient of linear expansion of iron is 10^–5 per C. The volume of an iron cube, 5 cm on edge, will increase by what amount if it is heated from 10C to 60C?

A) 0.00375 cm³

B) 0.1875 cm³

C) 0.0225 cm³

D) 0.0075 cm³

E) 0.0625 cm³

Difficulty: M

Section: 18-3

Learning Objective 18.3.3

35. The coefficient of linear expansion of steel is 11  10^–6 per C. A steel ball has a volume of exactly 100 cm³ at 0C. When heated to 100C, its volume becomes:

A) 100.33 cm³

B) 100. 11 cm³

C) 100.0011 cm³

D) 100.0033 cm³

E) none of these

Difficulty: M

Section: 18-3

Learning Objective 18.3.3

36. The coefficient of expansion of a certain type of steel is 0.000012 per C. The coefficient of volume expansion is:

A) (0.000012)³ (C)^–1

B) (4/3)(0.000012)³ (C)^–1

C) 3  0.000012 (C)^–1

D) 0.000012 (C)^–1

E) depends on the shape of the volume to which it will be applied

Difficulty: E

Section: 18-3

Learning Objective 18.3.3

37. Metal pipes, used to carry water, sometimes burst in the winter because:

A) metal contracts more than water

B) outside of the pipe contracts more than the inside

C) metal becomes brittle when cold

D) ice expands when it melts

E) water expands when it freezes

Difficulty: E

Section: 18-3

Learning Objective 18.3.3

38. A gram of distilled water at 4C:

A) will increase slightly in weight when heated to 6C

B) will decrease slightly in weight when heated to 6C

C) will increase slightly in volume when heated to 6C

D) will decrease slightly in volume when heated to 6C

E) will not change in either volume or weight

Difficulty: E

Section: 18-3

Learning Objective 18.3.3

39. A heat of transformation of a substance is:

A) the energy absorbed as heat during a phase transformation

B) the energy per unit mass absorbed as heat during a phase transformation

C) the same as the heat capacity

D) the same as the specific heat

E) the same as the molar specific heat

Difficulty: E

Section: 18-4

Learning Objective 18.4.0

40. The thermal energy of an object is associated with:

A) its kinetic energy

B) its potential energy

C) its inertia

D) the random motions of its molecules

E) the collective motions of its molecules

Difficulty: E

Section: 18-4

Learning Objective 18.4.1

41. Heat is:

A) energy transferred by virtue of a temperature difference

B) energy transferred by macroscopic work

C) energy content of an object

D) a temperature difference

E) a property objects have by virtue of their temperatures

Difficulty: E

Section: 18-4

Learning Objective 18.4.2

42. Heat has the same units as:

A) temperature

B) work

C) energy/time

D) heat capacity

E) energy/volume

Difficulty: E

Section: 18-4

Learning Objective 18.4.3

43. A calorie is about:

A) 0.24 J

B) 8.3 J

C) 250 J

D) 4.2 J

E) 4200 J

Difficulty: E

Section: 18-4

Learning Objective 18.4.3

44. An insulated container, filled with water, contains a thermometer and a paddle wheel. The paddle wheel can be rotated by an external source. This apparatus can be used to determine:

A) specific heat of water

B) relation between kinetic energy and absolute temperature

C) thermal conductivity of water

D) efficiency of changing work into heat

E) mechanical equivalent of heat

Difficulty: E

Section: 18-4

Learning Objective 18.4.4

45. The heat capacity of an object is:

A) the amount of heat energy to raise its temperature by 1C

B) the amount of heat energy to change its state without changing its temperature

C) the amount of heat energy per kilogram to raise its temperature by 1C

D) the ratio of its specific heat to that of water

E) the change in its temperature caused by adding 1 J of heat

Difficulty: E

Section: 18-4

Learning Objective 18.4.5

46. For constant volume processes the heat capacity of gas A is greater than the heat capacity of gas B. We conclude that when they both absorb the same energy as heat at constant volume:

A) the temperature of A increases more than the temperature of B

B) the temperature of B increases more than the temperature of A

C) the internal energy of A increases more than the internal energy of B

D) the internal energy of B increases more than the internal energy of A

E) A does more positive work than B

Difficulty: E

Section: 18-4

Learning Objective 18.4.5

47. The specific heat of a substance is:

A) the amount of heat energy to change the state of one gram of the substance

B) the amount of heat energy per unit mass emitted by oxidizing the substance

C) the amount of heat energy per unit mass to raise the substance from its freezing to its boiling point

D) the amount of heat energy per unit mass to raise the temperature of the substance by 1C

E) the temperature of the object divided by its mass

Difficulty: E

Section: 18-4

Learning Objective 18.4.6

48. Two different samples have the same mass and temperature. Equal quantities of energy are absorbed as heat by each. Their final temperatures may be different because the samples have different:

A) thermal conductivities

B) coefficients of expansion

C) densities

D) volumes

E) heat capacities

Difficulty: E

Section: 18-4

Learning Objective 18.4.6

49. The same energy Q enters five different substances as heat. Which of these has the greatest specific heat?

A) The temperature of 3 g of substance A increases by 10 K

B) The temperature of 4 g of substance B increases by 4 K

C) The temperature of 6 g of substance C increases by 15 K

D) The temperature of 8 g of substance D increases by 5 K

E) The temperature of 10 g of substance E increases by 10 K

Difficulty: E

Section: 18-4

Learning Objective 18.4.6

50. A cube of aluminum has an edge length of 20 cm. Aluminum has a density 2.7 times that of water (1 g/cm³) and a specific heat 0.217 times that of water (1 cal/gC˚). When the internal energy of the cube increases by 47000 cal its temperature increases by:

A) 5 C˚

B) 10 C˚

C) 20 C˚

D) 100 C˚

E) 200 C˚

Difficulty: M

Section: 18-4

Learning Objective 18.4.6

51. Take the mechanical equivalent of heat as 4 J/cal. A 10-gram bullet moving at 2000 m/s plunges into 1 kg of paraffin wax (specific heat 0.7 cal/g C). The wax was initially at 20C. Assuming that all the bullet's energy heats the wax, its final temperature is:

A) 20.14 C

B) 23.5 C

C) 20.006 C

D) 27.1 C

E) 48.6 C

Difficulty: M

Section: 18-4

Learning Objective 18.4.6

52. The energy given off by 300 grams of an alloy as it cools by 50C raises the temperature of 300 grams of water from 30C to 40C. The specific heat of the alloy is:

A) 5.0 cal/g C˚

B) 0.10 cal/g C˚

C) 0.15 cal/g C˚

D) 0.20 cal/g C˚

E) 0.50 cal/g C˚

Difficulty: M

Section: 18-4

Learning Objective 18.4.6

53. The specific heat of lead is 0.030 cal/g  C. 300 g of lead shot at 100C is mixed with 100 g of water at 70C in an insulated container. The final temperature of the mixture is:

A) 100C

B) 85.5C

C) 79.5C

D) 74.5C

E) 72.5C

Difficulty: M

Section: 18-4

Learning Objective 18.4.6

54. Object A, with heat capacity C_A and initially at temperature T_A, is placed in thermal contact with object B, with heat capacity C_B and initially at temperature T_B. The combination is thermally isolated. If the heat capacities are independent of the temperature and no phase changes occur, the final temperature of both objects is:

A) (C_AT_A – C_BT_B)/(C_A + C_B)

B) (C_AT_A + C_BT_B)/(C_A + C_B)

C) (C_AT_A – C_BT_B)/(C_A – C_B)

D) (C_A – C_B)T_A – T_B

E) (C_A + C_B)T_A – T_B

Difficulty: M

Section: 18-4

Learning Objective 18.4.6

55. The heat capacity of object B is twice that of object A. Initially A is at 300 K and B is at 450 K. They are placed in thermal contact and the combination is isolated. The final temperature of both objects is:

A) 300 K

B) 350 K

C) 400 K

D) 450 K

E) 600 K

Difficulty: M

Section: 18-4

Learning Objective 18.4.6

56. The three phases of matter are:

A) new, half, full

B) earth, air, fire

C) static, kinetic, potential

D) solid, liquid, gas

E) plasma, vapor, fluid

Difficulty: E

Section: 18-4

Learning Objective 18.4.7

57. The heat of fusion of water is 79.5 cal/g. This means 79.5 cal of energy are required to:

A) raise the temperature of 1 g of water by 1 K

B) turn 1 g of water to steam

C) raise the temperature of 1 g of ice by 1 K

D) melt 1 g of ice

E) increase the internal energy of 1 g of water by 1 J

Difficulty: E

Section: 18-4

Learning Objective 18.4.8

58. During the time that latent heat is involved in a change of state:

A) the temperature does not change

B) the substance always expands

C) a chemical reaction takes place

D) molecular activity remains constant

E) kinetic energy changes into potential energy

Difficulty: E

Section: 18-4

Learning Objective 18.4.8

59. The formation of ice from water is accompanied by:

A) absorption of energy as heat

B) temperature increase

C) decrease in volume

D) an evolution of heat

E) temperature decrease

Difficulty: E

Section: 18-4

Learning Objective 18.4.8

60. A metal sample of mass M requires a power input P to just remain molten. When the heater is turned off, the metal solidifies in a time T. The specific latent heat of fusion of this metal is:

A) P/MT

B) T/PM

C) PM/T

D) PMT

E) PT/M

Difficulty: M

Section: 18-4

Learning Objective 18.4.8

61. Solid A, with mass M, is at its melting point T_A. It is placed in thermal contact with solid B, with heat capacity C_B and initially at temperature T_B (T_B > T_A). The combination is thermally isolated. A has latent heat of fusion L and when it has melted has heat capacity C_A. If A completely melts the final temperature of both A and B is:

A) (C_AT_A + C_BT_B – ML)/(C_A + C_B)

B) (C_AT_A – C_BT_B + ML)/(C_A + C_B)

C) (C_AT_A – C_BT_B – ML)/(C_A + C_B)

D) (C_AT_A + C_BT_B + ML)/(C_A – C_B)

E) (C_AT_A + C_BT_B + ML)/(C_A – C_B)

Difficulty: M

Section: 18-4

Learning Objective 18.4.9

62. How many calories are required to change one gram of 0C ice to 100C steam? The latent heat of fusion is 80 cal/g and the latent heat of vaporization is 540 cal/g. The specific heat of water is 1.00 cal/g  K.

A) 100 cal

B) 540 cal

C) 620 cal

D) 720 cal

E) 900 cal

Difficulty: M

Section: 18-4

Learning Objective 18.4.9

63. Ten grams of ice at –20C is to be changed to steam at 130C. The specific heat of both ice and steam is 0.5 cal/g  C. The specific heat of water is 1.00 cal/g  K. The heat of fusion is 80 cal/g and the heat of vaporization is 540 cal/g. The entire process requires:

A) 750 cal

B) 1250 cal

C) 6950 cal

D) 7450 cal

E) 7700 cal

Difficulty: M

Section: 18-4

Learning Objective 18.4.9

64. Steam at 100C enters a radiator and leaves as water (at 80C). Take the heat of vaporization to be 540 cal/g. Of the total energy given off as heat, what percent arises from the cooling of the water?

A) 100%

B) 54%

C) 26%

D) 14%

E) 3.6%

Difficulty: M

Section: 18-4

Learning Objective 18.4.9

65. A certain humidifier operates by raising water to the boiling point and then evaporating it. Every minute 30 g of water at 20C are added to replace the 30 g that are evaporated. The heat of fusion of water is 333 kJ/kg, the heat of vaporization is 2256 kJ/kg, and the specific heat is 4190 J/kg How many joules of energy per minute does this humidifier require?

A) 4800 J/min

B) 18,600 J/min

C) 24,600 J/min

D) 77,700 J/min

E) 10,100,000 J/min

Difficulty: M

Section: 18-4

Learning Objective 18.4.9

66. Fifty grams of ice at 0C is placed in a thermos bottle containing one hundred grams of water at 6C. How many grams of ice will melt? The heat of fusion of water is 333 kJ/kg and the specific heat of water is 4190 J/kg  K.

A) 7.5 g

B) 2.0 g

C) 8.3 g

D) 17 g

E) 50 g

Difficulty: H

Section: 18-4

Learning Objective 18.4.9

67. Of the following which might NOT be zero over one cycle of a cyclic process?

A) the work done by the substance minus the energy absorbed by the substance as heat

B) the change in the pressure of the substance

C) the energy absorbed by the substance as heat

D) the change in the volume of the substance

E) the change in the temperature of the substance

Difficulty: E

Section: 18-5

Learning Objective 18.5.0

68. Pressure vs. volume graphs for a certain gas undergoing five different cyclic processes are shown below. During which cycle does the gas do the greatest positive work?

A) I

B) II

C) III

D) IV

E) V

Difficulty: E

Section: 18-5

Learning Objective 18.5.1

69. A gas:

A) does positive work as it expands.

B) does positive work as it contracts.

C) does no work if it expands adiabatically.

D) does negative work if it expands at constant pressure.

E) may do either positive or negative work as it expands, depending on the heat transfer.

Difficulty: E

Section: 18-5

Learning Objective 18.5.2

70. In the figure, a gas undergoes a transition from point A to point B along the path shown. How much work is done by the gas?

A) 10 kJ

B) 13 kJ

C) 23 kJ

D) –23 kJ

E) 0 kJ

Difficulty: M

Section: 18-5

Learning Objective 18.5.3

71. In the figure, what is the sign of the work done by the gas?

A) positive if the transition is A → B and negative if the transition is B → A

B) negative if the transition is A → B and positive if the transition is B → A

C) positive

D) negative

E) zero (no work is done)

Difficulty: E

Section: 18-5

Learning Objective 18.5.4

72. According to the first law of thermodynamics, applied to a gas, the increase in the internal energy during any process:

A) equals the heat input minus the work done on the gas

B) equals the heat input plus the work done on the gas

C) equals the work done on the gas minus the heat input

D) is independent of the heat input

E) is independent of the work done on the gas

Difficulty: E

Section: 18-5

Learning Objective 18.5.5

73. During an adiabatic process an object does 100 J of work and its temperature decreases by 5 K. During another process it does 25 J of work and its temperature decreases by 5 K. Its heat capacity for the second process is:

A) 20 J/K

B) 24 J/K

C) 5 J/K

D) 15 J/K

E) 100 J/K

Difficulty: E

Section: 18-5

Learning Objective 18.5.5

74. In a certain process a gas ends in its original thermodynamic state. Of the following, which is possible as the net result of the process?

A) It is adiabatic and the gas does 50 J of work

B) The gas does no work but absorbs 50 J of energy as heat

C) The gas does no work but rejects 50 J of energy as heat

D) The gas rejects 50 J of heat and does 50 J of work

E) The gas absorbs 50 J of energy as heat and does 50 J of work

Difficulty: E

Section: 18-5

Learning Objective 18.5.5

75. In the first law of thermodynamics, the sign of the heat transfer Q:

A) is positive if the system gives energy as heat to the environment and negative if it absorbs energy as heat from the environment

B) is negative if the system gives energy as heat to the environment and positive if it absorbs energy as heat from the environment

C) is always positive

D) is always negative

E) depends on the sign of the work being done

Difficulty: E

Section: 18-5

Learning Objective 18.5.6

76. In the first law of thermodynamics, the change in internal energy ΔE_int:

A) is always positive

B) is always negative

C) cannot be zero

D) tends to increase if heat energy is transferred to the gas, and tends to decrease if the gas does work on its environment

E) tends to decrease if heat energy is transferred to the gas, and tends to increase if the gas does work on its environment

Difficulty: E

Section: 18-5

Learning Objective 18.5.7

77. In an adiabatic process:

A) the energy absorbed as heat equals the work done by the system on its environment

B) the energy absorbed as heat equals the work done by the environment on the system

C) the energy absorbed as heat equals the change in internal energy

D) the work done by the environment on the system equals the change in internal energy

E) the work done by the system on its environment equals the change in internal energy

Difficulty: E

Section: 18-5

Learning Objective 18.5.8

78. A system undergoes an adiabatic process in which its internal energy increases by 20 J. Which of the following statements is true?

A) 20 J of work was done on the system

B) 20 J of work was done by the system

C) the system received 20 J of energy as heat

D) the system lost 20 J of energy as heat

E) none of the above are true

Difficulty: E

Section: 18-5

Learning Objective 18.5.8

79. In a constant-volume process with a gas,

A) no heat is exchanged with the environment

B) the internal energy of the gas does not change

C) the gas does no work

D) the pressure of the gas does not change

E) the temperature of the gas does not change

Difficulty: E

Section: 18-5

Learning Objective 18.5.9

80. Of the following which might NOT be zero over one cycle of a cyclic process?

A) the change in the internal energy of the substance

B) the change in pressure of the substance

C) the work done by the substance

D) the change in the volume of the substance

E) the change in the temperature of the substance

Difficulty: E

Section: 18-5

Learning Objective 18.5.10

81. In the free expansion of a gas,

A) the work done is zero but the heat transfer and change in internal energy may not be zero

B) the heat transfer is zero but the work done and the change in internal energy may not be zero

C) the change in internal energy is zero but the work done and the heat transfer may not be zero

D) the work done, the heat transfer, and the change in internal energy all may not be zero

E) the work done, the heat transfer, and the change in internal energy all are zero

Difficulty: E

Section: 18-5

Learning Objective 18.5.11

82. The units of thermal conductivity might be:

A) calcm/(sC)

B) cal/(cmsC)

C) cals/(cmC)

D) cmsC/cal

E) C/(calcms)

Difficulty: E

Section: 18-6

Learning Objective 18.6.0

83. Inside a room at a uniform comfortable temperature, metallic objects generally feel cooler to the touch than wooden objects do. This is because:

A) a given mass of wood contains more heat than the same mass of metal

B) metal conducts heat better than wood

C) heat tends to flow from metal to wood

D) the equilibrium temperature of metal in the room is lower than that of wood

E) the human body, being organic, resembles wood more closely than it resembles metal

Difficulty: E

Section: 18-6

Learning Objective 18.6.0

84. Which of the following statements pertaining to a vacuum flask (thermos) is NOT correct?

A) Silvering reduces radiation loss

B) Vacuum reduces conduction loss

C) Vacuum reduces convection loss

D) Vacuum reduces radiation loss

E) Glass walls reduce conduction loss

Difficulty: E

Section: 18-6

Learning Objective 18.6.0

85. A thermos bottle works well because:

A) its glass walls are thin

B) silvering reduces convection

C) vacuum reduces heat radiation

D) silver coating is a poor heat conductor

E) none of the above

Difficulty: E

Section: 18-6

Learning Objective 18.6.0

86. On a very cold day, a child puts his tongue against a fence post. It is much more likely that his tongue will stick to a steel post than to a wooden post. This is because:

A) steel has a higher specific heat

B) steel is a better radiator of heat

C) steel has a higher specific gravity

D) steel is a better heat conductor

E) steel is a highly magnetic material

Difficulty: E

Section: 18-6

Learning Objective 18.6.0

87. A slab of material has area A, thickness L, and thermal conductivity k. One of its surfaces (P) is maintained at temperature T₁ and the other surface (Q) is maintained at a lower temperature T₂. The rate of heat flow from P to Q is:

A) kA(T₁ – T₂)/L²

B) kL(T₁ – T₂)/A

C) kA(T₁ – T₂)/L

D) k(T₁ – T₂)/(LA)

E) LA(T₁ – T₂)/k

Difficulty: E

Section: 18-6

Learning Objective 18.6.1

88. The rate of heat flow by conduction through a slab does NOT depend upon the:

A) temperature difference between opposite faces of the slab

B) thermal conductivity of the slab

C) slab thickness

D) cross-sectional area of the slab

E) specific heat of the slab

Difficulty: E

Section: 18-6

Learning Objective 18.6.1

89. The rate of heat flow through a slab is P_cond. If the slab thickness is doubled, its cross-sectional area is halved, and the temperature difference across it is doubled, then the rate of heat flow becomes:

A) 2P_cond

B) P_cond/2

C) P_cond

D) P_cond/8

E) 8P_cond

Difficulty: M

Section: 18-6

Learning Objective 18.6.1

90. The diagram shows four slabs of different materials with equal thickness, placed side by side. Heat flows from left to right and the steady-state temperatures of the interfaces are given. Rank the materials according to their thermal conductivities, smallest to largest.

A) 1, 2, 3, 4

B) 2, 1, 3, 4

C) 1, 2, 4, 3

D) 3, 4, 2, 1

E) 4, 3, 2, 1

Difficulty: E

Section: 18-6

Learning Objective 18.6.1

91. The diagram shows four slabs of different materials with equal thickness, placed side by side. Heat flows from left to right and the steady-state temperatures of the interfaces are given. Rank the materials according to their rates of thermal conduction, smallest to largest.

A) 1, 2, 3, 4

B) 2, 1, 3, 4

C) 1, 2, 4, 3

D) 3, 4, 2, 1

E) all are equal

Difficulty: E

Section: 18-6

Learning Objective 18.6.2

92. A homeowner purchases insulation for her attic rated at R-15. She wants the attic insulated to R-30. If the insulation she purchased is 10 cm thick, what thickness does she need to use?

A) 10 cm

B) 15 cm

C) 20 cm

D) 30 cm

E) 40 cm

Difficulty: E

Section: 18-6

Learning Objective 18.6.3

93. Thermal energy can be transferred by convection:

A) only in solids

B) only in liquids

C) only in gases

D) through a vacuum

E) in either liquids or gases

Difficulty: E

Section: 18-6

Learning Objective 18.6.4

94. An iron stove, used for heating a room by radiation, is more efficient if:

A) its inner surface is highly polished

B) its inner surface is covered with aluminum paint

C) its outer surface is covered with aluminum paint

D) its outer surface is rough and black

E) its outer surface is highly polished

Difficulty: E

Section: 18-6

Learning Objective 18.6.5

95. An electric stove burner of diameter 20 cm is at a temperature of 250 °C. If σ = 5.67 x 10^-8 W/m²·K⁴, at what rate is the burner radiating energy? Assume the emissivity ε = 0.6.

A) 4 W

B) 80 W

C) 320 W

D) 1600 W

E) 8000 W

Difficulty: M

Section: 18-6

Learning Objective 18.6.6

96. To help keep buildings cool in the summer, dark colored window shades have been replaced by light colored shades. This is because light colored shades:

A) are more pleasing to the eye

B) absorb more sunlight

C) reflect more sunlight

D) transmit more sunlight

E) have a lower thermal conductivity

Difficulty: E

Section: 18-6

Learning Objective 18.6.7