COMPREHENSIVE EXAMINATION ON THERMODYNAMICS: AN ENGINEERING
APPROACH 10TH EDITION BY CENGEL, BOLES & KANOGLU
SECTION 1: INTRODUCTION AND BASIC CONCEPTS (Questions 1-10)
1. Which statement best expresses the second law of thermodynamics?
A) The temperature of a well-sealed room increases when a fan in the room is turned on
B) A cup of cool coffee in a warm room never gets hot by itself
C) Heat is generated when there is friction between two surfaces
D) A household refrigerator supplies heat to the kitchen when operating
Answer: B
Rationale: The second law states that heat cannot spontaneously flow from a colder body
to a hotter body without external work input. A cool coffee cup warming up by itself would
violate this principle, while the other options describe phenomena consistent with the first
law or practical applications.
2. What is the weight of an object with a mass of 10 kg at standard gravity?
A) 10 N
B) 10 lbf
C) 9 N
D) 98 N
Answer: D
Rationale: Weight is calculated as W = mg = (10 kg)(9.8 m/s²) = 98 kg·m/s² = 98 N. Since 1 N
,= 1 kg·m/s², option D is correct. Options A and C incorrectly use the numerical value of
mass as weight without applying gravity.
3. Which of the following is NOT a correct unit for work?
A) kg·m/s²
B) N·m
C) kPa·m³
D) kWh
Answer: A
Rationale: kg·m/s² is the unit for force (Newton), not work. Work units include N·m (Joule),
kPa·m³ (since Pa = N/m², multiplying by m³ gives N·m), and kWh (kilowatt-hour). Option A
represents force units, making it the incorrect choice for work.
4. Which properties are classified as intensive properties?
I. Volume
II. Density
III. Temperature
IV. Pressure
A) II and III
B) III and IV
C) I, II, and III
D) II, III, and IV
Answer: D
Rationale: Intensive properties are independent of the system's mass or size. Density,
temperature, and pressure are intensive properties. Volume is an extensive property as it
depends on the amount of mass present in the system.
5. Choose the WRONG statement regarding state and equilibrium:
A) A set of properties completely describes the state of a system
B) At a given state, all the properties of a system have fixed values
C) The state of a system only changes if the values of at least two properties change
D) In an equilibrium state, there are no driving forces within the system
,Answer: C
Rationale: A system's state changes if any property changes, not necessarily two
properties. A single property change, such as temperature alone at constant pressure,
constitutes a state change. Option C is incorrect, making it the wrong statement.
6. What is the specific volume of a fluid whose specific gravity is 1.25?
A) 1.25 m³/kg
B) 1250 m³/kg
C) 1/1.25 m³/kg
D) 1/1250 m³/kg
Answer: D
Rationale: ρ = SG × ρ_w = (1.25)(1000 kg/m³) = 1250 kg/m³. Specific volume v = 1/ρ =
1/(1250 kg/m³) = 1/1250 m³/kg. Option D correctly applies the density calculation and
specific volume relationship.
7. What is the specific weight of a fluid whose specific gravity is 1.0?
A) 1 N/m³
B) 9.8 N/m³
C) 10 N/m³
D) 9800 N/m³
Answer: D
Rationale: Specific weight = ρg = (1000 kg/m³)(9.8 m/s²) = 9800 kg·m/(m³·s²) = 9800 N/m³.
Since 1 N = 1 kg·m/s², the result is 9800 N/m³. Option D correctly calculates specific weight
for water.
8. Choose the WRONG statement regarding systems and control volumes:
A) The mass or region outside the system is called the surroundings
B) The real or imaginary surface separating system from surroundings is the boundary
C) The boundary has zero thickness and cannot contain any mass
D) The boundary of a system is fixed and cannot move
Answer: D
Rationale: System boundaries can be movable (e.g., piston-cylinder devices). A fixed
, boundary is not a requirement; boundaries may move, deform, or remain stationary. Option
D incorrectly states boundaries must be fixed.
9. A temperature change of 10°C is equal to:
A) 10 K
B) 273.15 K
C) 283.15 K
D) 263.15 K
Answer: A
Rationale: A change in Celsius temperature is equal to the change in Kelvin temperature
since both scales have the same magnitude. Therefore, ΔT = 10°C = 10 K. Options B, C, and
D represent absolute temperatures, not temperature changes.
10. Which unit conversion is correct for pressure?
A) 1 atm = 101.325 Pa
B) 1 atm = 101.325 kPa
C) 1 atm = 14.696 Pa
D) 1 bar = 100 Pa
Answer: B
Rationale: Standard atmospheric pressure is 101.325 kPa, which equals 101,325 Pa, 1 atm,
or 14.696 psi. Option B correctly states the atm to kPa conversion. Option A has incorrect
magnitude, C uses wrong units, and D is incorrect for bar conversion.
SECTION 2: ENERGY, ENERGY TRANSFER, AND GENERAL ENERGY ANALYSIS
(Questions 11-25)
11. The first law of thermodynamics for a closed system undergoing a process is
expressed as:
A) Q - W = ΔE
B) Q + W = ΔE
C) Q = W
D) ΔE = 0
APPROACH 10TH EDITION BY CENGEL, BOLES & KANOGLU
SECTION 1: INTRODUCTION AND BASIC CONCEPTS (Questions 1-10)
1. Which statement best expresses the second law of thermodynamics?
A) The temperature of a well-sealed room increases when a fan in the room is turned on
B) A cup of cool coffee in a warm room never gets hot by itself
C) Heat is generated when there is friction between two surfaces
D) A household refrigerator supplies heat to the kitchen when operating
Answer: B
Rationale: The second law states that heat cannot spontaneously flow from a colder body
to a hotter body without external work input. A cool coffee cup warming up by itself would
violate this principle, while the other options describe phenomena consistent with the first
law or practical applications.
2. What is the weight of an object with a mass of 10 kg at standard gravity?
A) 10 N
B) 10 lbf
C) 9 N
D) 98 N
Answer: D
Rationale: Weight is calculated as W = mg = (10 kg)(9.8 m/s²) = 98 kg·m/s² = 98 N. Since 1 N
,= 1 kg·m/s², option D is correct. Options A and C incorrectly use the numerical value of
mass as weight without applying gravity.
3. Which of the following is NOT a correct unit for work?
A) kg·m/s²
B) N·m
C) kPa·m³
D) kWh
Answer: A
Rationale: kg·m/s² is the unit for force (Newton), not work. Work units include N·m (Joule),
kPa·m³ (since Pa = N/m², multiplying by m³ gives N·m), and kWh (kilowatt-hour). Option A
represents force units, making it the incorrect choice for work.
4. Which properties are classified as intensive properties?
I. Volume
II. Density
III. Temperature
IV. Pressure
A) II and III
B) III and IV
C) I, II, and III
D) II, III, and IV
Answer: D
Rationale: Intensive properties are independent of the system's mass or size. Density,
temperature, and pressure are intensive properties. Volume is an extensive property as it
depends on the amount of mass present in the system.
5. Choose the WRONG statement regarding state and equilibrium:
A) A set of properties completely describes the state of a system
B) At a given state, all the properties of a system have fixed values
C) The state of a system only changes if the values of at least two properties change
D) In an equilibrium state, there are no driving forces within the system
,Answer: C
Rationale: A system's state changes if any property changes, not necessarily two
properties. A single property change, such as temperature alone at constant pressure,
constitutes a state change. Option C is incorrect, making it the wrong statement.
6. What is the specific volume of a fluid whose specific gravity is 1.25?
A) 1.25 m³/kg
B) 1250 m³/kg
C) 1/1.25 m³/kg
D) 1/1250 m³/kg
Answer: D
Rationale: ρ = SG × ρ_w = (1.25)(1000 kg/m³) = 1250 kg/m³. Specific volume v = 1/ρ =
1/(1250 kg/m³) = 1/1250 m³/kg. Option D correctly applies the density calculation and
specific volume relationship.
7. What is the specific weight of a fluid whose specific gravity is 1.0?
A) 1 N/m³
B) 9.8 N/m³
C) 10 N/m³
D) 9800 N/m³
Answer: D
Rationale: Specific weight = ρg = (1000 kg/m³)(9.8 m/s²) = 9800 kg·m/(m³·s²) = 9800 N/m³.
Since 1 N = 1 kg·m/s², the result is 9800 N/m³. Option D correctly calculates specific weight
for water.
8. Choose the WRONG statement regarding systems and control volumes:
A) The mass or region outside the system is called the surroundings
B) The real or imaginary surface separating system from surroundings is the boundary
C) The boundary has zero thickness and cannot contain any mass
D) The boundary of a system is fixed and cannot move
Answer: D
Rationale: System boundaries can be movable (e.g., piston-cylinder devices). A fixed
, boundary is not a requirement; boundaries may move, deform, or remain stationary. Option
D incorrectly states boundaries must be fixed.
9. A temperature change of 10°C is equal to:
A) 10 K
B) 273.15 K
C) 283.15 K
D) 263.15 K
Answer: A
Rationale: A change in Celsius temperature is equal to the change in Kelvin temperature
since both scales have the same magnitude. Therefore, ΔT = 10°C = 10 K. Options B, C, and
D represent absolute temperatures, not temperature changes.
10. Which unit conversion is correct for pressure?
A) 1 atm = 101.325 Pa
B) 1 atm = 101.325 kPa
C) 1 atm = 14.696 Pa
D) 1 bar = 100 Pa
Answer: B
Rationale: Standard atmospheric pressure is 101.325 kPa, which equals 101,325 Pa, 1 atm,
or 14.696 psi. Option B correctly states the atm to kPa conversion. Option A has incorrect
magnitude, C uses wrong units, and D is incorrect for bar conversion.
SECTION 2: ENERGY, ENERGY TRANSFER, AND GENERAL ENERGY ANALYSIS
(Questions 11-25)
11. The first law of thermodynamics for a closed system undergoing a process is
expressed as:
A) Q - W = ΔE
B) Q + W = ΔE
C) Q = W
D) ΔE = 0
