Thermodynamics Quiz

1. Real gases differ from ideal gases mainly because:

They follow Boyle’s law
Their molecules move randomly
They experience intermolecular attractions and have volume
Their pressure is always low

2. The two-phase region of a gas refers to:

Coexistence of liquid and vapor states
Region where gas is ideal
Solid and liquid equilibrium
Region of zero pressure

3. Critical constants (Pc, Vc, Tc) for gases indicate:

Ideal behavior of gases
Conditions at critical point for gas liquefaction
The point where gas behaves ideally at high pressure
Temperature where gas solidifies directly

4. The Van der Waals equation modifies ideal gas law by introducing:

Gravitational forces
Electric forces
Correction for molecular attraction and volume
Magnetic forces

5. What happens at temperatures above the critical temperature?

Gas cannot be liquefied by pressure alone
Gas behaves ideally
Gas solidifies immediately
Gas volume becomes zero

6. Limitations of Van der Waals equation are evident particularly at:

Moderate pressures and temperatures
Ideal conditions only
Conditions well-predicted by ideal gas law
High pressures and very low temperatures

7. Van der Waals isotherms show a flat region indicating:

Gas behavior at high temperatures
Solid phase
Phase transition between liquid and vapor
Infinite compressibility of gas

8. The critical state in gases refers to:

Gas at maximum volume
Unique conditions of pressure, volume, and temperature at which gas and liquid phases become indistinguishable
Lowest possible temperature
Highest possible pressure

9. What exactly does Andrew's experiment demonstrate?

Behavior of ideal gases under low pressures
Critical phenomena and gas liquefaction in real gases
Molecular diffusion rates of gases
Ideal gas law validity under high temperature

10. What does Andrew's experiment involve?

Measuring pressure using air as a manometer ✅
Measuring temperature changes in ideal gases
Measuring the speed of gas molecules
Determining molecular weights of gases

11. A thermodynamic system refers to:

A region or quantity of matter chosen for study
The entire universe excluding surroundings
Only gases undergoing expansion
A solid-liquid boundary

12. Surroundings in thermodynamics typically mean:

Internal components of a system
Everything external to the system boundaries
The internal energy of the system
Part of the system under high pressure

13. An intensive thermodynamic variable is:

Volume
Temperature
Mass
Internal energy

14. The zeroth law of thermodynamics defines:

Conservation of energy
Thermal equilibrium between systems
Entropy of isolated systems
Relationship between heat and work

15. Thermodynamic equilibrium means:

No net flow of energy or matter
Continuous energy exchange
Maximum pressure state
Minimum temperature state

16. A reversible thermodynamic process:

Occurs infinitely slowly through equilibrium states
Occurs spontaneously
Cannot be returned to original state
Always increases entropy drastically

17. An irreversible process is characterized by:

Constant entropy
Equilibrium at every step
Generation of entropy
No net change in state variables

18. An equation of state relates:

Pressure, volume, and temperature
Energy and work only
Mass and volume only
Temperature and entropy only

19. Expansivity (\(\beta\)) measures how much:

Volume changes with temperature at constant pressure
Pressure changes with volume
Temperature changes with entropy
Mass changes with pressure

20. Compressibility (\(\kappa\)) is defined as:

Change in entropy with temperature
Change in volume with pressure at constant temperature
Change in temperature with pressure
Change in mass with volume

21. Internal energy of an ideal gas depends upon:

Pressure only
Volume only
Temperature only
Both pressure and volume

22. In thermodynamics, heat is defined as:

Energy transfer due to temperature difference
Energy stored due to volume
Work done by the system
Total internal energy

23. Work done by a gas expanding against external pressure is:

Always zero
Always positive
Positive if system expands
Negative if system expands

24. In a cyclic process, the net change in internal energy of a system is:

Maximum
Minimum
Always positive
Always zero

25. The first law of thermodynamics is a statement of:

Entropy conservation
Conservation of energy
Mass conservation
Heat transfer only

26. Heat capacity of a substance is defined as:

Amount of heat needed to raise its temperature by one degree
Energy stored at constant pressure only
Work done during expansion
Internal energy change only

27. Difference between \( C_p \) and \( C_v \) for an ideal gas equals:

\( R/2 \)
Gas constant \( R \)
Zero
\( 2R \)

28. Indicator diagram (P–V diagram) represents:

Heat absorbed by system
Work done by or on the system
Entropy changes only
Internal energy changes only

29. Work done in reversible isothermal expansion of an ideal gas is given by:

\(W = nRT\)
\(W = P(V_2 - V_1)\)
\(W = nRT \ln\frac{V_2}{V_1}\)
\(W = 0\)

30. Work done in reversible adiabatic expansion of an ideal gas results in:

Increase in internal energy
Decrease in internal energy
No change in internal energy
Infinite heat absorption

31. The Kelvin-Planck statement of the second law states that:

Heat can flow spontaneously from cold to hot
It is impossible to convert all heat absorbed into work completely
Internal energy always decreases
Entropy of isolated systems decreases

32. A heat engine operates between two reservoirs by:

Absorbing heat from a hot reservoir and releasing part to a cold reservoir
Absorbing heat from a cold reservoir only
Converting work completely into heat
Rejecting heat only to a hot reservoir

33. Thermal efficiency of a heat engine is defined as:

Ratio of heat rejected to heat absorbed
Ratio of work output to heat absorbed
Ratio of heat absorbed to work input
Difference of temperatures only

34. Carnot's engine is an ideal heat engine that:

Has zero efficiency
Has the maximum possible efficiency between two temperatures
Converts all heat absorbed into work completely
Operates without heat absorption

35. Work done by a Carnot engine per cycle is given by:

Zero
Total heat absorbed only
Difference between heat absorbed and rejected
Sum of absorbed and rejected heat

36. Reversibility in thermodynamics means:

Processes increase entropy drastically
Processes are spontaneous and irreversible
Processes occur at infinite speed
Processes occur without entropy production

37. A Carnot refrigerator operates by:

Transferring heat spontaneously from hot to cold
Transferring heat from a cold reservoir to a hot reservoir by consuming work
Producing maximum work output
Operating without work input

38. A heat pump is a device that:

Converts heat directly into work completely
Transfers heat from cold to hot reservoir using work
Only absorbs heat from hot reservoir
Only rejects heat to a cold reservoir

39. Carnot’s theorem states that:

No engine between two reservoirs is more efficient than a Carnot engine
All engines have equal efficiency
Engines can have 100% efficiency at low temperature
Entropy always decreases in isolated systems

40. Clausius-Clapeyron equation relates:

Heat absorbed and work done only
Efficiency and temperature difference
Change in vapor pressure and temperature to latent heat
Internal energy and entropy

41. Maxwell's thermodynamic relations are derived from:

Conservation of mass
Zeroth law of thermodynamics
Exactness of thermodynamic differentials
First law only

42. TdS equations connect:

Changes in entropy with temperature, volume, and pressure
Mass with volume changes
Pressure with mass and density
Only temperature and energy

43. The fundamental thermodynamic energy equation for internal energy (U) is:

dU = PdV - TdS
dU = TdS - PdV
dU = VdP + SdT
dU = SdT - VdP

44. Heat capacity at constant volume (C_V) is given by:

(∂U/∂P)_V
(∂S/∂T)_P
(∂U/∂T)_V
(∂V/∂T)_P

45. Heat capacity at constant pressure (C_P) is expressed as:

(∂H/∂T)_P
(∂U/∂T)_P
(∂S/∂P)_T
(∂V/∂T)_S

46. Gibbs free energy (G) is defined thermodynamically as:

G = U - TS
G = H - TS
G = U + PV
G = T + PV

47. Which thermodynamic function measures the useful work obtainable at constant temperature and pressure?

Helmholtz free energy
Gibbs free energy
Internal energy
Entropy

48. The third law of thermodynamics states:

Entropy always increases spontaneously
Entropy approaches zero as temperature approaches absolute zero
Internal energy remains constant at absolute zero
Heat cannot flow from cold to hot spontaneously

49. Helmholtz free energy (F) is defined as:

F = U - TS
F = H + TS
F = U + PV
F = G + PV

50. The Clapeyron equation specifically describes:

Pressure-volume relation for ideal gases
Internal energy and entropy at absolute zero
Relationship between vapor pressure and temperature for phase transitions
Entropy change at constant volume

51. Heat transfer by conduction occurs through:

Electromagnetic waves
Movement of fluid molecules
Direct molecular collisions
Gravitational forces

52. Thermal conductivity (\(k\)) is highest in:

Gases
Metals
Liquids
Vacuum

53. Lee’s disc experiment is primarily used to measure:

Heat radiation
Heat convection
Thermal conductivity of poor conductors
Specific heat capacity

54. Thermal resistance in conduction is defined as:

Ratio of temperature difference to heat flow rate
Ratio of heat flow rate to temperature difference
Rate of heat flow per unit area
Rate of temperature change per unit mass

55. Thermal radiation differs from conduction and convection because:

It occurs only in fluids
It requires a medium
It does not require any medium
It only happens at high pressure

56. Radiant intensity is defined as:

Radiant energy emitted per unit solid angle
Total energy radiated per unit area
Energy radiated per unit volume
Heat flow per unit time

57. Radiant emittance is the:

Energy radiated in all directions per unit solid angle
Radiant energy emitted per unit surface area per unit time
Total energy emitted per unit mass
Energy radiated per unit length

58. According to Stefan’s law, total energy radiated by a blackbody is proportional to:

T²
T³
T⁴
T⁵

59. The Stefan-Boltzmann law can be mathematically written as:

E = σT⁴
E = σT³
E = σT²
E = σT

60. Thermal conductivity of a poor conductor (insulator) is typically measured by:

Searle’s method
Lee’s disc method
Joule’s calorimeter method
Newton’s cooling method

61. A microstate in statistical mechanics represents:

A complete specification of all particle positions and momenta
Only the total energy of the system
The overall volume of the system
A state defined by macroscopic properties only

62. Phase space in statistical mechanics is defined as:

A space of energies only
A space describing pressure and volume only
A multidimensional space of positions and momenta
A space with only particle velocities

63. Density of states refers to:

Number of particles per unit volume
Number of accessible states per unit energy range
Total number of particles in a system
Energy per particle

64. Gamma (Γ) space is associated with:

Phase space of the entire system
Phase space for a single particle
Momentum space only
Position space only

65. Principle of equal a priori probabilities assumes:

Lower energy states are more probable
Higher energy states dominate equilibrium
All accessible microstates are equally probable at equilibrium
Probability depends on external fields only

66. Ergodic hypothesis suggests that:

Systems spontaneously move to lower energy
Time averages equal ensemble averages
Systems never reach equilibrium
Microstates change only at absolute zero

67. Canonical ensemble describes a system with fixed:

Energy, volume, and number of particles
Temperature, volume, and number of particles
Temperature, pressure, and energy
Volume, energy, and temperature

68. Partition function (Z) in canonical ensemble is defined as:

Sum of energy states
Sum over states of \( e^{-E/kT} \)
Total energy multiplied by temperature
Product of energy and entropy

69. Grand canonical ensemble allows exchange of:

Volume and temperature only
Energy and particles with reservoir
Only energy
Only particles

70. Equipartition theorem states that each quadratic energy degree of freedom contributes:

\( kT \) to total energy
\( 3kT/2 \) to total energy
\( kT/2 \) to total energy
\( kT/4 \) to total energy

71. Maxwell-Boltzmann statistics applies to:

Electrons
Classical distinguishable particles
Bosons
Photons only

72. Fermi-Dirac statistics applies to particles that:

Have integer spin
Obey the Pauli exclusion principle
Are indistinguishable bosons
Have zero rest mass

73. Bose-Einstein statistics describe the distribution of:

Bosons
Electrons in metals
Classical gases
Fermions

74. Maxwell-Boltzmann distribution assumes particles are:

Quantum indistinguishable
Classical and distinguishable
Fermions
Always at absolute zero

75. In Fermi-Dirac distribution, occupancy of energy states is limited by:

Pauli exclusion principle
Temperature only
Pressure
Volume of container

76. According to Bose-Einstein statistics, particles can occupy:

At most one particle per state
Only energy states above a certain threshold
The same quantum state without limit
States limited strictly by spin

77. The Maxwell-Boltzmann distribution describes particle distribution in terms of:

Speeds and energies at thermal equilibrium
Spin and angular momentum
Quantum numbers only
Zero energy states only

78. The Fermi energy represents:

Energy at absolute zero for bosons
Highest occupied energy state at absolute zero for fermions
Energy of photons at equilibrium
Average energy per particle

79. Bose-Einstein condensation occurs when bosons:

Occupy the lowest quantum state at very low temperatures
Achieve maximum energy state
Behave like fermions
Become distinguishable

80. At high temperature and low density, all distributions (Maxwell-Boltzmann, Fermi-Dirac, Bose-Einstein) approach:

Bose-Einstein distribution
Fermi-Dirac distribution
Maxwell-Boltzmann distribution
Zero energy distribution

81. Which gas law combines Boyle’s, Charles’, and Gay-Lussac’s laws?

Ideal gas law
Dalton’s law
Graham’s law
Avogadro’s law

82. In an adiabatic process, which quantity remains constant?

Temperature
Pressure
Heat exchange
Volume

83. Heat always flows spontaneously from:

Hot body to cold body
Cold body to hot body
Low pressure to high pressure
Low volume to high volume

84. Carnot engine efficiency depends only on:

Temperatures of hot and cold reservoirs
Pressure and volume of gas
Amount of gas
Type of gas

85. Third law of thermodynamics states entropy at absolute zero is:

Infinite
Zero
Maximum
Negative

86. Which particles obey Fermi-Dirac statistics?

Bosons
Fermions
Photons
Classical particles

87. Unit of thermal conductivity is:

J·kg⁻¹·K⁻¹
J·s⁻¹
W·m⁻¹·K⁻¹
J·m⁻²·K⁻¹

88. Equipartition theorem assigns how much energy per degree of freedom?

kT/2
kT
3kT/2
kT/4

89. Absolute zero temperature corresponds to:

0 K
-273 K
273°C
0°C

90. Van der Waals equation corrects for:

Molecular attraction and volume
Ideal gas behavior
Zero pressure
Absolute zero

91. If a Carnot engine operates between temperatures 600 K and 300 K, its maximum efficiency is:

25%
33%
50%
75%

92. The internal energy U of an ideal monoatomic gas of N particles at temperature T is given by:

\( \frac{3}{2}NkT \)
\( NkT \)
\( \frac{5}{2}NkT \)
\( \frac{1}{2}NkT \)

93. For a reversible isothermal expansion of 1 mole of an ideal gas at 300 K from 2 liters to 4 liters, the work done is approximately:

345 J
718 J
1728 J
1382 J

94. The partition function Z for two distinguishable particles each with two energy states (0 and ε) at temperature T is:

\( (1+e^{-ε/kT})^2 \)
\( 1+2e^{-ε/kT}+e^{-2ε/kT} \)
\( e^{-ε/kT}+e^{-2ε/kT} \)
\( 2+2e^{-ε/kT} \)

95. Entropy change (ΔS) for melting 1 kg of ice at 0°C (Latent heat = 334 kJ/kg) is:

1200 J/K
1225 J/K
1400 J/K
1670 J/K

96. For a given Maxwell velocity distribution, the most probable speed (v_mp) is related to average speed (v̅) by:

\( v_{mp} < \bar{v} \)
\( v_{mp} = \bar{v} \)
\( v_{mp} > \bar{v} \)
No fixed relation

97. Bose-Einstein condensation occurs significantly at:

Very low temperature and high particle density
High temperature only
Low pressure and high temperature
Room temperature only

98. Fermi energy in metals typically has the order of magnitude:

Electron-volts (eV)
Joules (J)
milli-electron-volts (meV)
kilo-electron-volts (keV)

99. Clausius-Clapeyron equation is primarily used to:

Predict vapor-pressure variation with temperature
Find internal energy at absolute zero
Determine heat capacity at constant volume
Calculate thermal conductivity

100. Ergodic hypothesis relates ensemble averages to:

Time averages of a single system
Spatial averages only
Quantum states averages
Thermodynamic potentials