Chapter 10: Thermal Properties of Matter Assertion-Reason Questions | physics Class 11 CBSE

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 1

Logic Check

Assertion (A): A gas thermometer gives the same temperature reading regardless of which gas is used at low density. Reason (R): All low-density gases obey the same ideal gas law PV = μRT and exhibit identical expansion behaviour.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 2

Logic Check

Assertion (A): Water contracts when heated from 0°C to 4°C. Reason (R): The coefficient of volume expansion of water is negative between 0°C and 4°C.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 3

Logic Check

Assertion (A): The temperature of a substance remains constant during its change of state. Reason (R): The heat supplied during a change of state goes into changing the kinetic energy of the molecules.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): Cooking is slower at high altitudes. Reason (R): At high altitudes, atmospheric pressure is lower, which reduces the boiling point of water.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 5

Logic Check

Assertion (A): Steam burns are more dangerous than boiling water burns at 100°C. Reason (R): Steam at 100°C has more heat energy than water at 100°C by an amount equal to the latent heat of vaporisation.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 6

Logic Check

Assertion (A): Radiation can transfer heat through vacuum. Reason (R): Radiation transfers energy through electromagnetic waves, which do not require a material medium for propagation.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): A body with large reflectivity is a poor emitter of radiation. Reason (R): A good reflector is a poor absorber, and by Kirchhoff's law, a good absorber is also a good emitter.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 8

Logic Check

Assertion (A): The triple point of water is preferred over the ice point as a thermometric fixed point. Reason (R): The triple point of water occurs at a unique, reproducible temperature and pressure, unlike the ice point which depends on external atmospheric pressure.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 9

Logic Check

Assertion (A): In a Dewar flask, the space between the double walls is evacuated. Reason (R): Evacuation reduces heat transfer by conduction and convection between the walls.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 10

Logic Check

Assertion (A): The coefficient of volume expansion of an ideal gas decreases with increasing temperature. Reason (R): For an ideal gas at constant pressure, αV = 1/T, so αV is inversely proportional to absolute temperature.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 11

Logic Check

Assertion (A): Lakes and ponds freeze from the top, not the bottom, in winter. Reason (R): Water has its maximum density at 4°C; below 4°C, water becomes less dense and remains at the surface, where it eventually freezes.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 12

Logic Check

Assertion (A): Metals are good conductors of heat. Reason (R): In metals, heat is conducted only through molecular collisions, which occur more frequently than in non-metals.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 13

Logic Check

Assertion (A): The boiling point of water decreases when external pressure is reduced. Reason (R): At reduced pressure, water molecules require less energy (lower temperature) to escape from the liquid surface as vapour.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 14

Logic Check

Assertion (A): Convection is possible only in fluids, not in solids. Reason (R): Convection requires bulk movement of matter, which is possible only in liquids and gases where molecules can move freely.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 15

Logic Check

Assertion (A): A blacksmith heats an iron ring before fitting it on a wooden wheel rim. Reason (R): On heating, the iron ring contracts, creating a tight fit around the wheel rim when cooled.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 16

Logic Check

Assertion (A): Water is used as a coolant in automobile radiators. Reason (R): Water has the highest specific heat capacity among common substances, allowing it to absorb large amounts of heat with minimal temperature rise.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 17

Logic Check

Assertion (A): The graph of loge(T₂–T₁) versus time during Newton's law of cooling verification is a straight line with negative slope. Reason (R): According to Newton's law, dT₂/dt = –K(T₂–T₁), which on integration gives loge(T₂–T₁) = –Kt + c.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 18

Logic Check

Assertion (A): The coefficient of linear expansion of copper is approximately five times that of pyrex glass. Reason (R): Metals generally have higher coefficients of linear expansion than glass because metallic bonds are weaker than covalent bonds in glass.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 19

Logic Check

Assertion (A): The temperature of ice remains 0°C while it is melting, even though heat is continuously being supplied. Reason (R): Heat supplied to melting ice goes entirely into increasing the temperature of the water formed.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 20

Logic Check

Assertion (A): In a pressure cooker, food cooks faster than in an open vessel. Reason (R): Increased pressure inside a pressure cooker raises the boiling point of water, enabling cooking at temperatures above 100°C.

Reasoning Options

ByteNotes

Chapter sections

Chapter 10: Thermal Properties of Matter | Assertion-Reason

Assertion (A): A gas thermometer gives the same temperature reading regardless of which gas is used at low density. Reason (R): All low-density gases obey the same ideal gas law PV = μRT and exhibit identical expansion behaviour.

Assertion (A): Water contracts when heated from 0°C to 4°C. Reason (R): The coefficient of volume expansion of water is negative between 0°C and 4°C.

Assertion (A): The temperature of a substance remains constant during its change of state. Reason (R): The heat supplied during a change of state goes into changing the kinetic energy of the molecules.

Assertion (A): Cooking is slower at high altitudes. Reason (R): At high altitudes, atmospheric pressure is lower, which reduces the boiling point of water.

Assertion (A): Steam burns are more dangerous than boiling water burns at 100°C. Reason (R): Steam at 100°C has more heat energy than water at 100°C by an amount equal to the latent heat of vaporisation.

Assertion (A): Radiation can transfer heat through vacuum. Reason (R): Radiation transfers energy through electromagnetic waves, which do not require a material medium for propagation.

Assertion (A): A body with large reflectivity is a poor emitter of radiation. Reason (R): A good reflector is a poor absorber, and by Kirchhoff's law, a good absorber is also a good emitter.

Assertion (A): The triple point of water is preferred over the ice point as a thermometric fixed point. Reason (R): The triple point of water occurs at a unique, reproducible temperature and pressure, unlike the ice point which depends on external atmospheric pressure.

Assertion (A): In a Dewar flask, the space between the double walls is evacuated. Reason (R): Evacuation reduces heat transfer by conduction and convection between the walls.

Assertion (A): The coefficient of volume expansion of an ideal gas decreases with increasing temperature. Reason (R): For an ideal gas at constant pressure, αV = 1/T, so αV is inversely proportional to absolute temperature.

Assertion (A): Lakes and ponds freeze from the top, not the bottom, in winter. Reason (R): Water has its maximum density at 4°C; below 4°C, water becomes less dense and remains at the surface, where it eventually freezes.

Assertion (A): Metals are good conductors of heat. Reason (R): In metals, heat is conducted only through molecular collisions, which occur more frequently than in non-metals.

Assertion (A): The boiling point of water decreases when external pressure is reduced. Reason (R): At reduced pressure, water molecules require less energy (lower temperature) to escape from the liquid surface as vapour.

Assertion (A): Convection is possible only in fluids, not in solids. Reason (R): Convection requires bulk movement of matter, which is possible only in liquids and gases where molecules can move freely.

Assertion (A): A blacksmith heats an iron ring before fitting it on a wooden wheel rim. Reason (R): On heating, the iron ring contracts, creating a tight fit around the wheel rim when cooled.

Assertion (A): Water is used as a coolant in automobile radiators. Reason (R): Water has the highest specific heat capacity among common substances, allowing it to absorb large amounts of heat with minimal temperature rise.

Assertion (A): The graph of loge(T₂–T₁) versus time during Newton's law of cooling verification is a straight line with negative slope. Reason (R): According to Newton's law, dT₂/dt = –K(T₂–T₁), which on integration gives loge(T₂–T₁) = –Kt + c.

Assertion (A): The coefficient of linear expansion of copper is approximately five times that of pyrex glass. Reason (R): Metals generally have higher coefficients of linear expansion than glass because metallic bonds are weaker than covalent bonds in glass.

Assertion (A): The temperature of ice remains 0°C while it is melting, even though heat is continuously being supplied. Reason (R): Heat supplied to melting ice goes entirely into increasing the temperature of the water formed.

Assertion (A): In a pressure cooker, food cooks faster than in an open vessel. Reason (R): Increased pressure inside a pressure cooker raises the boiling point of water, enabling cooking at temperatures above 100°C.

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