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#	Question	Answer
1	Is thermodynamics a microscopic or macroscopic science?	Macroscopic. It deals with bulk systems and does not go into the molecular constitution of matter.
2	What thermodynamic variable is defined by the Zeroth law?	Temperature.
3	Is internal energy a state variable?	Yes. It depends only on the state of the system, not on the path taken to reach that state.
4	What is specific heat capacity?	\( s = \frac{1}{m} \frac{\Delta Q}{\Delta T} \).
5	What is the specific heat capacity of water in SI units?	4186 J kg⁻¹ K⁻¹.
6	What is an isothermal process?	A process in which the temperature of the system remains constant.
7	What is the work done by an ideal gas in an adiabatic process?	\( W = \frac{\mu R(T_1 - T_2)}{\gamma - 1} \).
8	What are the conditions for a process to be reversible?	It must be quasi-static and free from dissipative effects.
9	What is the relation between heat absorbed and heat rejected in a Carnot engine?	\( \frac{Q_1}{Q_2} = \frac{T_1}{T_2} \).
10	What is the molar specific heat capacity of a solid according to the law of equipartition?	\( 3R \).
11	A cylinder contains 3 moles of hydrogen at STP. The gas is compressed adiabatically to half its original volume. By what factor does the pressure increase? (γ for H₂ = 1.4)	2.64.
12	Is a bullet's temperature related to its own high speed (bulk motion) when fired from a gun?	No — temperature relates to a body's internal (disordered) energy, not the kinetic energy of its centre-of-mass motion. The bullet's temperature rises only when it decelerates (e.g. striking wood) and its ordered KE converts to internal energy.
13	What was the old 'caloric' theory of heat, discarded in favour of the modern energy concept?	Heat was thought to be an invisible fluid ('caloric') that flowed from a colder to a hotter body on contact, similar to water levelling between two connected tanks, until the 'caloric levels' (temperatures) equalised.
14	What is the molar specific heat capacity at constant volume, \(C_v\), in terms of internal energy?	\( C_v = (\Delta U/\Delta T)_v \), since at constant volume all the heat absorbed goes into changing internal energy.
15	Why does a book lying on a table never spontaneously jump up, even though this wouldn't violate the First Law of Thermodynamics?	Because it would require the table to spontaneously cool, converting internal energy entirely into the book's mechanical energy — a process forbidden by the Second Law of Thermodynamics, even though energy conservation alone would allow it.
16	0.1 g of water at 100°C becomes 167.1 cc of steam at atmospheric pressure (\(1.013\times10^5\) Pa), absorbing 54 cal of heat. What is the change in internal energy?	≈209 J, from \(\Delta U=\Delta Q-P\Delta V\): \(\Delta Q\approx225.7\) J, \(P\Delta V\approx16.9\) J — the same method as this chapter's own water-vaporisation calculation. (NEET 2018)
17	An ideal gas and a real gas both expand isothermally. How does the change in internal energy compare?	For the ideal gas, \(\Delta U=0\) (internal energy depends only on temperature). For the real gas, \(\Delta U\neq0\), since intermolecular forces mean its internal energy also depends on volume/separation, which changes during expansion. (AIPMT 1993)
18	During an adiabatic process, pressure and temperature are found to satisfy \(P\propto T^3\). What is \(\gamma\) for this gas?	\(\gamma=3/2\), from \(T^\gamma P^{1-\gamma}=\text{constant}\Rightarrow T\propto P^{(\gamma-1)/\gamma}\), and matching \(T\propto P^{1/3}\) gives \((\gamma-1)/\gamma=1/3\). (AIPMT 2013)
19	A monatomic gas at pressure P, volume V expands isothermally to 2V, then adiabatically to 16V. What is the final pressure? (\(\gamma=5/3\))	P/64. Isothermal step: \(P_1=P/2\) (Boyle's law). Adiabatic step: \(P_f=P_1(2V/16V)^\gamma=(P/2)(1/8)^{5/3}=(P/2)(1/32)\). (AIPMT 2014)
20	A scientist claims to have built an engine with 26% efficiency operating between 400 K and 300 K. Is this possible?	No — the maximum (Carnot) efficiency between these temperatures is \(1-300/400=25\%\); no real engine can exceed it. (AIPMT 2001)
21	How much heat is needed to raise the temperature of 1 g of helium (monatomic, molar mass 4 g/mol, \(C_v=3R/2\)) from \(T_1\) to \(T_2\) at constant volume?	\(Q\approx(3R/8)(T_2-T_1)\), since \(\mu=1/4\) mol and \(Q=\mu C_v\Delta T\). (AIPMT 2013)