Thermodynamics: Master the Laws of Heat and Energy

Question 1

According to the second law of thermodynamics, which of the following is true?

Accepted Answer

The entropy of an isolated system always increases with time.

Answer

All natural processes are reversible.

Answer

The entropy of an isolated system never changes.

Answer

The amount of energy in the universe is decreasing.

Question 2

What is the entropy of a perfect crystal at absolute zero in kelvins?

Accepted Answer

Zero

Answer

Infinity

Answer

Undefined

Answer

Equal to the Boltzmann constant

Question 3

Which statement best reflects the Clausius statement of the second law of thermodynamics?

Accepted Answer

Heat cannot flow from a colder to a hotter reservoir without external work being done.

Answer

An isolated system's entropy never decreases.

Answer

All heat engines operating between given temperatures have identical efficiencies.

Answer

The Carnot cycle has the highest possible efficiency among heat engines.

Question 4

During an isothermal process, what happens to the entropy of the system?

Accepted Answer

Remains constant

Answer

Increases

Answer

Decreases

Answer

Becomes negative

Question 5

Which property describes an ideal gas?

Accepted Answer

Molecules have negligible volume.

Answer

Molecules have strong interactions.

Answer

Molecules move in circular paths.

Answer

Molecules have constant velocity.

Question 6

Which of the following is the SI unit of entropy?

Accepted Answer

Joule per Kelvin

Answer

Joule

Answer

Kelvin

Answer

Kelvin per Joule

Question 7

Which of the following statements about entropy is true?

Accepted Answer

Entropy is a measure of the randomness of a system.

Answer

Entropy always decreases in an isolated system.

Answer

Entropy is conserved in closed systems.

Answer

Entropy can only be positive.

Question 8

What is the second law of thermodynamics?

Accepted Answer

Entropy always increases in an isolated system, approaching a maximum value.

Answer

Heat flows from hot objects to cold objects.

Answer

The total energy of an isolated system remains constant.

Answer

The efficiency of a heat engine can never be 100%.

Question 9

Which of the following has the highest specific heat capacity?

Accepted Answer

Water

Answer

Air

Answer

Wood

Answer

Metal

Question 10

Which of the following is NOT considered a thermodynamic system?

Accepted Answer

The Milky Way galaxy

Answer

A sealed container containing a gas

Answer

A piston-cylinder assembly

Answer

A person in a closed room

Question 11

The first law of thermodynamics states that:

Accepted Answer

The total energy of an isolated system remains constant

Answer

Energy can be created or destroyed

Answer

Heat always flows from hot to cold

Answer

Entropy always increases

Question 12

A heat engine is a device that:

Accepted Answer

Converts heat into mechanical work

Answer

Converts work into heat

Answer

Stores thermal energy

Answer

Transfers thermal energy

Question 13

Which of the following is a source of irreversible heat transfer?

Accepted Answer

Friction

Answer

Conduction

Answer

Convection

Answer

Radiation

Question 14

The efficiency of a heat engine is defined as:

Accepted Answer

Work output / Heat input

Answer

Heat input / Work output

Answer

Entropy change / Temperature

Answer

Temperature / Entropy change

Question 15

A heat engine operates between hot and cold reservoirs at 600 K and 300 K, respectively. What is the maximum possible efficiency of this engine?

Accepted Answer

Approximately 66.7%

Answer

Less than 20%

Answer

50%

Answer

Greater than 100%

Question 16

Which of the following is the unit of entropy?

Accepted Answer

Joules per Kelvin

Answer

Joules

Answer

Pascals

Answer

Kelvin

Question 17

What is the key distinction between heat and work in thermodynamics?

Accepted Answer

Heat is transferred due to a temperature difference, while work is transferred by a force acting through a distance.

Answer

Heat is transferred by a force acting through a distance, while work is transferred due to a temperature difference.

Answer

Heat and work are identical concepts.

Answer

Heat always flows from a hot object to a cold object, unlike work.

Question 18

A heat engine operates between a hot reservoir at 500 K and a cold reservoir at 300 K. To maximize its efficiency, what type of cycle should the engine operate on?

Accepted Answer

Carnot cycle

Answer

Rankine cycle

Answer

Brayton cycle

Answer

Stirling cycle

Question 19

Which of the following processes involves no heat transfer between the system and its surroundings?

Accepted Answer

Adiabatic

Answer

Isothermal

Answer

Isobaric

Answer

Isochoric

Question 20

The first law of thermodynamics states that:

Accepted Answer

Energy can neither be created nor destroyed, only transferred or transformed.

Answer

Entropy always increases in a closed system.

Answer

Heat engines can operate at 100% efficiency.

Answer

The universe is expanding.

Question 21

Which of the following is NOT a consequence of the second law of thermodynamics?

Accepted Answer

Energy can be created or destroyed.

Answer

Entropy always increases in a closed system.

Answer

Heat flows spontaneously from hot to cold.

Answer

The universe is constantly changing.

Question 22

Which of the following accurately describes the first law of thermodynamics?

Accepted Answer

The internal energy of a system changes due to the difference between heat added and work done.

Answer

Heat can spontaneously flow from a colder to a hotter body.

Answer

The entropy of an isolated system always decreases over time.

Answer

The efficiency of a heat engine can exceed 100%.

Question 23

Which of the following is the mathematical representation of the first law of thermodynamics?

Accepted Answer

ΔU = Q + W

Answer

Q = ΔU - W

Answer

W = Q + ΔU

Answer

ΔU = W - Q

Question 24

In an irreversible process within an isolated system, the entropy of the system:

Accepted Answer

Grows

Answer

Diminishes

Answer

Remains unchanged

Answer

Cannot be determined

Question 25

Which thermodynamic process occurs when the pressure of a system remains constant?

Accepted Answer

Isobaric

Answer

Isothermal

Answer

Adiabatic

Answer

Isochoric

Question 26

What is the significance of the zeroth law of thermodynamics?

Accepted Answer

It establishes thermal equilibrium as a transitive property

Answer

It defines the concept of absolute zero

Answer

It provides the basis for temperature measurement

Answer

It predicts the direction of heat flow

Question 27

State the first law of thermodynamics.

Accepted Answer

The total energy of an isolated system remains constant

Answer

Heat energy can be completely converted into mechanical energy

Answer

Entropy of a system always increases with time

Answer

Heat engines have 100% efficiency

Question 28

Which of these processes is reversible?

Accepted Answer

Expansion of an ideal gas

Answer

Burning of fossil fuels

Answer

Melting of ice

Answer

Freezing of water

Question 29

Calculate the change in entropy of a system that absorbs heat Q at constant temperature T.

Accepted Answer

Q/T

Answer

T/Q

Answer

-Q/T

Answer

-T/Q

Question 30

Identify the entity that is NOT considered a thermodynamic system.

Accepted Answer

An athlete engaging in physical activity

Answer

A sealed container filled with gas

Answer

A piston and cylinder setup

Answer

A device designed for heat exchange

Question 31

Define the quantity known as entropy.

Accepted Answer

A measure of system disorder

Answer

A measure of system energy

Answer

A measure of system temperature

Answer

A measure of system pressure

Question 32

What is the defining characteristic of a Carnot heat engine's efficiency?

Accepted Answer

Dependence on reservoir temperatures

Answer

A constant value of 100%

Answer

A value less than 100%

Answer

A value greater than 100%

Question 33

Which process exemplifies an increase in entropy?

Accepted Answer

Vaporization of liquid water

Answer

Solidification of liquid water

Answer

Condensation of water vapor

Answer

Freezing of liquid water

Question 34

Which system exhibits a decrease in entropy?

Accepted Answer

Closed system undergoing adiabatic compression

Answer

Closed system undergoing isothermal expansion

Answer

Open system exchanging heat with surroundings

Answer

Isolated system undergoing chemical reaction

Question 35

During an isothermal process, which of the following remains **constant**?

Accepted Answer

Temperature

Answer

Heat transferred into the system

Answer

Work done by the system

Answer

Entropy

Question 36

Which of the following processes is **reversible**?

Accepted Answer

Expansion of a gas into a vacuum

Answer

Adiabatic compression of a gas

Answer

Stirring a cup of coffee

Answer

Burning of fossil fuels

Question 37

Which of the following is a direct consequence of the second law of thermodynamics?

Accepted Answer

Entropy of the universe always increases.

Answer

Heat cannot flow spontaneously from a cold reservoir to a hot reservoir.

Answer

All heat engines have an efficiency of 100%.

Answer

Perpetual motion machines are possible.

Question 38

What is the entropy change of a system that absorbs heat Q at a **constant** temperature T?

Accepted Answer

Q / T

Answer

-Q / T

Answer

Q * T

Answer

-Q * T

Question 39

Which of the following is **not** a factor affecting the efficiency of a heat engine?

Accepted Answer

Mass of the piston

Answer

Temperature of the heat source

Answer

Temperature of the heat sink

Answer

Type of working fluid

Question 40

How is the molar specific heat capacity of a gas related to its degrees of freedom?

Accepted Answer

Specific heat capacity is directly proportional to degrees of freedom.

Answer

Specific heat capacity is inversely proportional to degrees of freedom.

Answer

Specific heat capacity is independent of degrees of freedom.

Answer

Specific heat capacity is equal to degrees of freedom.

Question 41

Entropy is a measure of the disorder or randomness of a system. Which of the following statements best describes the relationship between entropy and the number of microstates of a system?

Accepted Answer

Entropy is proportional to the number of microstates.

Answer

Entropy is inversely proportional to the number of microstates.

Answer

Entropy is independent of the number of microstates.

Answer

Entropy is inversely proportional to the square root of the number of microstates.

Question 42

Thermodynamic systems can be classified as open, closed, or isolated. Which of the following systems is an example of an open system?

Accepted Answer

A beaker of water that is open to the atmosphere

Answer

A sealed bottle of perfume

Answer

A closed container of gas

Answer

A refrigerator

Question 43

Which process involves a gas expanding while maintaining a constant temperature?

Accepted Answer

Isothermal process

Answer

Adiabatic process

Answer

Isochoric process

Answer

Isobbaric process

Question 44

During a reversible process, the entropy change of the system is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Indeterminate

Question 45

Which type of heat engine exhibits the highest theoretical efficiency?

Accepted Answer

Carnot engine

Answer

Otto cycle engine

Answer

Diesel cycle engine

Answer

Stirling engine

Question 46

The relationship between heat capacity (C) and specific heat capacity (c) is:

Accepted Answer

C = mc

Answer

c = MC

Answer

C = c/m

Answer

c = m/C

Question 47

The fundamental difference between heat and work is that:

Accepted Answer

Heat is energy transfer due to temperature difference, while work involves a force acting through a distance.

Answer

Heat is always positive, while work can be either positive or negative.

Answer

Heat can only occur between objects in contact, while work can be done remotely.

Answer

Heat is a scalar quantity, while work is a vector quantity.

Question 48

An adiabatic process is characterized by:

Accepted Answer

No heat transfer between the system and its surroundings

Answer

Constant volume throughout the process

Answer

Constant temperature throughout the process

Answer

Zero entropy change

Question 49

According to the first law of thermodynamics, what remains constant in an isolated system?

Accepted Answer

Total energy

Answer

Heat

Answer

Entropy

Answer

Efficiency

Question 50

Which of the following processes is considered reversible in thermodynamics?

Accepted Answer

Expansion of a gas into a vacuum

Answer

Melting of a solid

Answer

Flow of heat through a non-ideal conductor

Answer

Chemical reaction in an open system

Question 51

Which of the following is NOT a factor that affects the efficiency of a heat engine?

Accepted Answer

Size of the engine (number of cylinders)

Answer

Temperature difference between the reservoirs

Answer

Type of working fluid

Answer

Presence of friction

Question 52

What is the primary function of a condenser in a heat engine cycle?

Accepted Answer

To remove heat from the working fluid

Answer

To convert heat into work

Answer

To increase the pressure of the working fluid

Answer

To decrease the volume of the working fluid