Heat and Thermodynamics MCQs 2026

In an isochoric (isovolumetric) process, the quantity that remains constant is

1. A volume ✓
2. B pressure ✓
3. C temperature ✓
4. D heat ✓

In an isobaric process, the quantity that remains constant is

1. A volume ✓
2. B pressure ✓
3. C temperature ✓
4. D entropy ✓

In an adiabatic process, there is

1. A no change in temperature ✓
2. B no change in pressure ✓
3. C no heat exchange with the surroundings ✓
4. D no change in internal energy ✓

In an isothermal process, the

1. A pressure remains constant ✓
2. B volume remains constant ✓
3. C heat exchange is zero ✓
4. D temperature remains constant ✓

Entropy is best understood as a measure of

1. A the disorder or randomness of a system ✓
2. B the total heat content of a system ✓
3. C the temperature of a system ✓
4. D the pressure of a system ✓

The second law of thermodynamics implies that

1. A energy can be created from nothing ✓
2. B heat always flows spontaneously from a colder body to a hotter one ✓
3. C heat cannot spontaneously flow from a colder body to a hotter one without external work ✓
4. D entropy of an isolated system always decreases ✓

According to the first law of thermodynamics, the change in internal energy of a system equals

1. A work done by the system only ✓
2. B heat added only ✓
3. C zero for any process ✓
4. D heat added to the system minus work done by the system ✓

The first law of thermodynamics is essentially a statement of

1. A increasing entropy ✓
2. B conservation of energy ✓
3. C zero heat transfer ✓
4. D absolute zero being unreachable ✓

The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then

1. A they are in thermal equilibrium with each other ✓
2. B they must have equal masses ✓
3. C they must have equal volumes ✓
4. D heat automatically flows between them ✓

The zeroth law of thermodynamics establishes the concept of

1. A energy conservation ✓
2. B entropy ✓
3. C temperature and thermal equilibrium ✓
4. D absolute zero only ✓

When a solid is heated, its dimensions generally

1. A decrease ✓
2. B increase, due to thermal expansion ✓
3. C remain exactly the same ✓
4. D become zero ✓

The technique used to measure the heat exchanged in physical or chemical processes is called

1. A thermography ✓
2. B pyrometry ✓
3. C barometry ✓
4. D calorimetry ✓

During a change of state, such as melting or boiling, the temperature of the substance

1. A remains constant until the change is complete ✓
2. B increases steadily ✓
3. C decreases steadily ✓
4. D fluctuates randomly ✓

The heat energy required to change a substance from solid to liquid, or liquid to gas, at constant temperature is called

1. A specific heat ✓
2. B sensible heat ✓
3. C latent heat ✓
4. D radiant heat ✓

The specific heat capacity of water is unusually

1. A very low compared to most substances ✓
2. B equal to that of iron ✓
3. C equal to that of air ✓
4. D very high compared to most common substances ✓

The amount of heat required to raise the temperature of a unit mass of a substance by one degree is called its

1. A latent heat ✓
2. B specific heat capacity ✓
3. C thermal conductivity ✓
4. D heat capacity of the container ✓

Temperature is best described as

1. A a measure of the average kinetic energy of the molecules of a substance ✓
2. B the total heat energy contained in a body ✓
3. C the same as heat energy ✓
4. D always constant for all substances ✓

Heat is best described as

1. A the temperature of a body ✓
2. B a measure of average kinetic energy of molecules ✓
3. C a property stored permanently in a body ✓
4. D energy transferred between bodies due to a temperature difference ✓

The freezing point of water on the Fahrenheit scale is

1. A 0 degrees Fahrenheit ✓
2. B 100 degrees Fahrenheit ✓
3. C 32 degrees Fahrenheit ✓
4. D 273 degrees Fahrenheit ✓

The normal boiling point of water on the Celsius scale, at standard atmospheric pressure, is

1. A 100 degrees Celsius ✓
2. B 0 degrees Celsius ✓
3. C 212 degrees Celsius ✓
4. D 373 degrees Celsius ✓

Zero on the Kelvin scale, known as absolute zero, corresponds to approximately

1. A 0 degrees Celsius ✓
2. B -273.15 degrees Celsius ✓
3. C 100 degrees Celsius ✓
4. D -100 degrees Celsius ✓

Metals are generally good conductors of heat because they contain

1. A tightly bound electrons ✓
2. B free (mobile) electrons that readily transfer thermal energy ✓
3. C no electrons at all ✓
4. D very heavy nuclei ✓

A material with very low thermal conductivity, often used for insulation, is

1. A glass wool or a similar insulating material ✓
2. B copper ✓
3. C silver ✓
4. D aluminum ✓

The Stefan-Boltzmann law states that the power radiated by a black body per unit area is proportional to

1. A the temperature ✓
2. B the square of the temperature ✓
3. C the fourth power of the absolute temperature ✓
4. D the square root of the temperature ✓

According to Wien's displacement law, as the temperature of a black body increases, the wavelength of peak emission

1. A increases ✓
2. B decreases ✓
3. C remains constant ✓
4. D becomes infinite ✓

A perfect black body is defined as an object that

1. A reflects all radiation falling on it ✓
2. B emits no radiation at all ✓
3. C is always black in visible color ✓
4. D absorbs all incident radiation and is also the best possible emitter ✓

The triple point of water, at which solid, liquid, and gaseous water coexist in equilibrium, occurs at a unique

1. A temperature and pressure ✓
2. B volume only ✓
3. C density only ✓
4. D mass only ✓

An engine that converts heat energy into mechanical work by using the temperature difference between a hot source and a cold sink is called a

1. A refrigerator ✓
2. B calorimeter ✓
3. C heat engine ✓
4. D thermometer ✓

The latent heat of vaporization of water at standard atmospheric pressure is approximately

1. A 2260 kJ/kg ✓
2. B 334 kJ/kg ✓
3. C 4.2 kJ/kg ✓
4. D 100 kJ/kg ✓

The latent heat of fusion of ice at 0 degrees Celsius is approximately

1. A 2260 kJ/kg ✓
2. B 4.2 kJ/kg ✓
3. C 100 kJ/kg ✓
4. D 334 kJ/kg ✓

A thermos flask (vacuum flask) minimizes heat loss mainly by reducing

1. A chemical reactions ✓
2. B conduction, convection, and radiation losses via a vacuum layer and reflective walls ✓
3. C the specific heat of its contents ✓
4. D the mass of the liquid stored ✓

Thermal equilibrium between two bodies in contact is reached when

1. A both bodies attain the same temperature and no net heat flows between them ✓
2. B one body has zero temperature ✓
3. C both bodies have the same mass ✓
4. D both bodies have the same specific heat ✓

No heat engine can convert 100% of the absorbed heat into useful work, a consequence of

1. A the second law of thermodynamics ✓
2. B the zeroth law of thermodynamics ✓
3. C Boyle's law ✓
4. D Charles's law ✓

The specific heat capacity of water, approximately 4200 joules per kilogram per kelvin, means water

1. A heats up and cools down very quickly compared to most substances ✓
2. B requires a relatively large amount of heat energy to change its temperature ✓
3. C cannot store any thermal energy ✓
4. D has zero thermal conductivity ✓

Sublimation refers to the direct change of state from

1. A liquid to gas ✓
2. B gas to liquid ✓
3. C solid directly to gas, without passing through the liquid state ✓
4. D solid to liquid ✓

The change of a gas directly into a solid, without passing through the liquid state, is called

1. A evaporation ✓
2. B condensation ✓
3. C fusion ✓
4. D deposition ✓

Evaporation differs from boiling in that evaporation

1. A occurs only at the boiling point ✓
2. B can occur at any temperature, from the liquid's surface only ✓
3. C occurs throughout the entire volume of liquid ✓
4. D requires no energy input ✓

The process by which a vapor changes back into a liquid is called

1. A fusion ✓
2. B sublimation ✓
3. C condensation ✓
4. D vaporization ✓

The SI unit of temperature is the

1. A Celsius ✓
2. B Fahrenheit ✓
3. C Rankine ✓
4. D Kelvin ✓

A Carnot engine is an idealized heat engine that operates on a cycle consisting of

1. A two isothermal and two isobaric processes ✓
2. B four adiabatic processes ✓
3. C two isobaric and two isochoric processes ✓
4. D two isothermal and two adiabatic processes ✓

The efficiency of a Carnot engine depends only on

1. A the working substance used ✓
2. B the size of the engine ✓
3. C the temperatures of the hot and cold reservoirs ✓
4. D the pressure of the gas ✓

No real heat engine can be more efficient than a Carnot engine operating between the same two temperatures, a statement related to the

1. A zeroth law ✓
2. B second law of thermodynamics ✓
3. C law of conservation of mass ✓
4. D ideal gas law ✓

A refrigerator works by

1. A creating cold energy from nothing ✓
2. B destroying heat energy ✓
3. C converting all heat into work ✓
4. D using external work to transfer heat from a colder region to a hotter region ✓

Boyle's law states that, at constant temperature, the pressure of a fixed mass of gas is

1. A inversely proportional to its volume ✓
2. B directly proportional to its volume ✓
3. C independent of its volume ✓
4. D proportional to the square of its volume ✓

Charles's law states that, at constant pressure, the volume of a fixed mass of gas is

1. A inversely proportional to its absolute temperature ✓
2. B independent of temperature ✓
3. C directly proportional to its absolute temperature ✓
4. D proportional to the square of temperature ✓

Gay-Lussac's law states that, at constant volume, the pressure of a fixed mass of gas is

1. A inversely proportional to its absolute temperature ✓
2. B directly proportional to its absolute temperature ✓
3. C independent of temperature ✓
4. D inversely proportional to volume ✓

The ideal gas equation is generally written as

1. A PV = nRT/2 ✓
2. B P + V = nRT ✓
3. C PV^2 = nRT ✓
4. D PV = nRT ✓

Heat transfer through a solid medium, without bulk movement of the material, is called

1. A conduction ✓
2. B convection ✓
3. C radiation ✓
4. D evaporation ✓

Heat transfer through the actual bulk movement of a heated fluid, liquid or gas, is called

1. A conduction ✓
2. B radiation ✓
3. C convection ✓
4. D sublimation ✓

Heat transfer that can occur even through a vacuum, via electromagnetic waves, is called

1. A conduction ✓
2. B convection ✓
3. C diffusion ✓
4. D radiation ✓