What does Kinetic Theory cover for NEET Physics?

9 lessons: Avogadro Number, Concept of Pressure Kinetic Theory, Degrees of Freedom, Equation of State Perfect Gas, Equipartition Energy, Kinetic Interpretation Temperature, Kinetic Theory Assumptions, Mean Free Path and RMS Speed Gas.

How often has Kinetic Theory come up in NEET past papers?

Our set of verified past papers has 7 questions from this unit, from NEET 2020, 2022, 2023, 2025 and 2026. Each is answered against the official NTA key.

Is the Kinetic Theory material free?

Yes. All 9 lessons and 72 practice questions are free, with no login needed.

Kinetic Theory

9 lessons

Topic index in NCERT order

9 of 9 lessons by the NCERT chapter they teach from, in book order. The page is the first printed page of your NCERT book the lesson cites; PYQs are the past NEET questions on that topic.

Class 11 Physics, Chapter 12

Avogadro Numberp. 2461 PYQ
Equation of State Perfect Gasp. 2471 PYQ
Kinetic Theory Assumptionsp. 2480 PYQs
Concept of Pressure Kinetic Theoryp. 2500 PYQs
Degrees of Freedomp. 2521 PYQ
Equipartition Energyp. 2521 PYQ
Mean Free Pathp. 2552 PYQs
Kinetic Interpretation Temperaturep. 2560 PYQs
RMS Speed Gasp. 2561 PYQ

Avogadro Number

8 MCQs1 PYQs6 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Concept of Pressure Kinetic Theory

8 MCQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (2)

Degrees of Freedom

8 MCQs1 PYQs2 revision cardsWorked example

Easy Recall (4)Direct Application (2)Concept Trap (1)Calculation (1)

Equation of State Perfect Gas

8 MCQs1 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (2)

Equipartition Energy

8 MCQs1 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (2)

Kinetic Interpretation Temperature

8 MCQs4 revision cardsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Kinetic Theory Assumptions

8 MCQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Mean Free Path

8 MCQs2 PYQs2 revision cardsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

RMS Speed Gas

8 MCQs1 PYQs4 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (2)

Past-paper questions from this unit

7 questions from NEET 2020, 2022, 2023, 2025, 2026. Answers verified against NTA official keys.

By year in our set: 2020 (2) · 2022 (1) · 2023 (1) · 2025 (1) · 2026 (2)

Lesson: Mean Free Path

NEET 2026

The mean free path of molecules in an ideal gas A is half that of another ideal gas B. The diameter of the spherical molecules of gas A is twice the diameter of the molecules of B. If number densities of the gases A and B are n_A and n_B, respectively, then the correct option is :

1n_A = n_B

2n_A = 2n_B

3n_A = (1/4) n_B

4n_A = (1/2) n_B

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Lesson: Degrees of Freedom

NEET 2026

An ideal gas is made of polyatomic molecules. Each of the molecules has three translational, three rotational and f number of vibrational modes. If the ratio of heat capacities C_P/C_V of the gas is 8/7, then the value of f is :

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Equation of State Perfect Gas

NEET 2025

An oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to 11 atmospheric pressures at temperature 27°C. The mass of the oxygen withdrawn from the cylinder is nearly equal to: [Given, R = 100/12 J mol⁻¹ K⁻¹, and molecular mass of O₂ = 32, 1 atm pressure = 1.01 × 10⁵ N/m]

10.156 kg

20.125 kg

30.144 kg

40.116 kg

NTA Answer: Option 4(final)

Report an error · Every fix is public: corrections log

Lesson: RMS Speed Gas

NEET 2023

The temperature of a gas is –50°C. To what temperature the gas should be heated so that the rms speed is increased by 3 times?

13295°C

23097 K

3223 K

4669°C

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Avogadro Number

NEET 2022

The volume occupied by the molecules contained in 4.5 kg water at STP, if the intermolecular forces vanish away is

15.6 m³

25.6 × 10⁶ m³

35.6 × 10³ m³

45.6 × 10⁻³ m³

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Equipartition Energy

NEET 2020

The average thermal energy for a mono-atomic gas is : (k_B is Boltzmann constant and T, absolute temperature)

17/2 k_BT

21/2 k_BT

33/2 k_BT

45/2 k_BT

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Lesson: Mean Free Path

NEET 2020

The mean free path for a gas, with molecular diameter d and number density n can be expressed as :

11/(√2 n²π²d²)

21/(√2 nπd)

31/(√2 nπd²)

41/(√2 n²πd²)

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Exam traps and common mistakes in this unit

Lesson: RMS Speed Gas

Trap

v_rms vs T: linear vs sqrt scaling

Category: Similar Terms

Student treats v_rms ∝ T instead of √T. Doubling T does NOT double v_rms; it multiplies by √2.

When it triggers

Question asks for new v_rms after T change.

How to avoid

v_rms = √(3RT/M). v_rms ∝ √T. To double v_rms, T must quadruple.

Lesson: RMS Speed Gas

Mistake

Scales v_rms linearly with T instead of √T.

Root cause: formula misuse

Correction

v_rms = √(3RT/M), so v_rms ∝ √T. To double v_rms, T must quadruple (factor of 4). Common error: assume doubling T doubles v_rms.

Formulas in this unit

Lesson: Degrees of Freedom

Cv from degrees of freedom

C_{v} = \frac{f}{2} R

Each quadratic DoF contributes (1/2)R to molar Cv. Mono: f=3, Cv=3R/2; di-rigid: f=5, Cv=5R/2; poly-rigid: f=6, Cv=3R.

Symbol	Quantity	SI Unit
Cv	molar specific heat	J/mol/K
f	degrees of freedom	-
R	gas constant	J/mol/K

Valid when

Equipartition holds (temperature high enough)
Quadratic energy modes

Lesson: Equation of State Perfect Gas

Ideal gas equation

P V = n R T = N k T

Fundamental equation of state of ideal gas relating pressure, volume, temperature.

Symbol	Quantity	SI Unit
P	pressure	Pa
V	volume	m^3
n	moles	mol
R	8.314	J/mol/K
N	molecule count	-
k	Boltzmann 1.38e-23	J/K
T	temp	K

Valid when

Gas obeys ideal gas approximation (low pressure, high temperature relative to phase transitions)

Lesson: Equipartition Energy

Average translational KE per molecule

⟨ K E ⟩ = \frac{3}{2} k T

Microscopic interpretation of temperature: T is direct measure of average translational kinetic energy.

Symbol	Quantity	SI Unit
k	Boltzmann constant	J/K
T	absolute temperature	K

Valid when

Translational degrees of freedom only
Ideal gas

Lesson: Kinetic Interpretation Temperature

RMS speed of gas molecules

v_{rms} = \frac{3 R T}{M} = \frac{3 k T}{m}

Root-mean-square molecular speed; depends on T and molar mass M (or molecular mass m).

Symbol	Quantity	SI Unit
R	gas constant	J/mol/K
T	temp	K
M	molar mass	kg/mol
k	Boltzmann	J/K
m	molecular mass	kg

Valid when

Ideal gas
Maxwell-Boltzmann distribution

Lesson: Mean Free Path

Mean free path of gas molecule

λ = \frac{1}{2 π n d ^{2}}

Average distance between successive molecular collisions.

Symbol	Quantity	SI Unit
lambda	mean free path	m
n	number density	1/m^3
d	molecular diameter	m

Valid when

Hard-sphere model
Equilibrium gas

NEET question patterns in this unit

Lesson: Equation of State Perfect Gas

PV = nRT. Given two of (P, V, T, n) and changes, find missing.

Multi StepEasy

Common distractors

forgets temperature conversion

Mixes °C with K

Lesson: Equipartition Energy

Average translational KE per molecule = (3/2)kT (monoatomic). Total via DoF.

Direct ApplicationEasy

Common distractors

uses 3 2 RT not 3 2 kT

Confuses per-mole RT with per-molecule kT

Lesson: Mean Free Path

Mean free path scaling with n, d. lambda = 1/(sqrt(2)pin*d^2).

InterpretationEasy

Common distractors

ignores d squared

Treats d linearly

Lesson: RMS Speed Gas

Find new T given v_rms scales by factor k. v_rms ∝ sqrt(T), so T_new = T*k^2.

Multi StepMedium

Common distractors

uses linear scaling

Treats v_rms ∝ T not sqrt(T)

Questions about this unit

What does Kinetic Theory cover for NEET Physics?: 9 lessons: Avogadro Number, Concept of Pressure Kinetic Theory, Degrees of Freedom, Equation of State Perfect Gas, Equipartition Energy, Kinetic Interpretation Temperature, Kinetic Theory Assumptions, Mean Free Path and RMS Speed Gas.
How often has Kinetic Theory come up in NEET past papers?: Our set of verified past papers has 7 questions from this unit, from NEET 2020, 2022, 2023, 2025 and 2026. Each is answered against the official NTA key.
Is the Kinetic Theory material free?: Yes. All 9 lessons and 72 practice questions are free, with no login needed.