Heat and Thermodynamics NEET PYQs (2000–2026)

Solved Heat and Thermodynamics PYQs

3 recent questions with answers. The full set of 97 is free to practise.

1. NEET 2026EasyIdeal Gas Laws
   Q1

   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:

   • A4
   • B3
   • C2
   • D1

   Show answer & solution

   Correct answer: (A)

   For polyatomic gas,
   
   $C_V=\frac{3}{2}R+\frac{3}{2}R+fR=(3+f)R$.
   
   $C_P=C_V+R=(4+f)R$.
   
   $\frac{C_P}{C_V}=\frac{4+f}{3+f}=\frac{8}{7}$.
   
   $$7(4+f)=8(3+f)$$
   
   $$\Rightarrow 28+7f=24+8f$$
   
   $\Rightarrow f=4$.
2. NEET 2026EasyThermal Expansion
   Q2

   The temperature of a metallic sphere of radius $R$ is increased by a small amount $\Delta T$. If the linear coefficient of thermal expansion of the metal is $\alpha$, the approximate increase in the
   
   volume of the sphere is:

   • A$2\pi R^3\alpha \Delta T$
   • B$3\pi R^3\alpha \Delta T$
   • C$4\pi R^3\alpha \Delta T$
   • D$6\pi R^3\alpha \Delta T$

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   Correct answer: (C)

   Volume expansion coefficient $\gamma =3\alpha$.
   
   $\Delta V=V_0\gamma \Delta T=\frac{4}{3}\pi R^3\times 3\alpha \Delta T=4\pi R^3\alpha \Delta T$.
3. NEET 2026EasyWork Done by a Gas
   Q3

   In an adiabatic expansion, the temperature of one mole of an ideal monatomic gas $(\gamma =5/3)$ decreases from $60K$ to $50K$. The work done by the gas in the process is:(Take the universal gas constant as $R=8.3Jmo{l}^{-1}{K}^{-1}$)

   • A41.5 J
   • B83 J
   • C124.5 J
   • D166 J

   Show answer & solution

   Correct answer: (C)

   For adiabatic process, $Q=0$. First law: $\Delta U=-W$ (work done
   
   by gas).
   
   $$\Delta U=n{C}_V\left(T_2-T_1\right)=1\times \frac{R}{\gamma -1}(50-60)=\frac{8.3}{2/3}\times (-10)=12.45\times (-10)=-124.5$$
   
   J.
   
   $W=-\Delta U=124.5$ J.

Topic-wise question count

Where NEET has asked from Heat and Thermodynamics, most frequent first.

• First Law of Thermodynamics and its Applications42
• Ideal Gas Laws (Boyle's Law, Charles's Law, Gay-Lussac's Law, Ideal Gas Equation)25
• Internal Energy of a Gas9
• Work Done by a Gas7
• Specific Heat Capacity and Latent Heat4
• Ideal Gas Laws3
• Heat Transfer (Conduction, Convection, Radiation)3
• Thermal Expansion2
• First Law of Thermodynamics1
• Newton's Law of Cooling1

Year-wise Heat and Thermodynamics questions in NEET

Number of questions from this chapter in each year's paper(s).