Here is a strange fact about the NEET syllabus: thermodynamics appears twice. Once in Physics, once in Chemistry, taught by different teachers, from different books, often months apart — and most students never realise they’re studying the same laws.

That’s the opportunity, and it’s what makes thermodynamics for NEET 2027 unusually efficient. Thermodynamics for NEET 2027 is one body of physics wearing two uniforms. Learn the shared core once and you cut your workload nearly in half, while fixing the single confusion that costs the most marks: the two subjects use opposite sign conventions.

Set this against the physics strategy and the physical chemistry approach, since this chapter sits in both.

The Shared Core

Both subjects rest on the same first law of thermodynamics NEET builds on: energy is conserved, it just moves between internal energy, heat and work. Keep it in spaced revision that sticks once you’ve got it.

The concepts are identical across both: system and surroundings, the types of system (open, closed, isolated), state functions versus path functions, and the distinction between reversible and irreversible processes. Internal energy, enthalpy, entropy and Gibbs free energy are the same quantities in both papers.

If you’ve understood these in Chemistry, you already understand them in Physics. Nobody tells students this, so they learn it twice. Use subject-wise chapter weightage to see how the load splits, then study the overlap as one unit.

The Sign Convention Trap

This is the single most important paragraph in the article, so read it twice.

Physics and Chemistry define the work term with opposite signs. The first law of thermodynamics NEET tests is written ΔU = Q − W in Physics and ΔU = Q + W in Chemistry, because each defines W differently — Physics as work done by the system, Chemistry as work done on the system.

Get this wrong and every numerical comes out with a flipped sign. The fix isn’t to memorise both blindly; it’s to know which convention you’re in before you write anything. If the question is Physics-flavoured — gases, engines, PV diagrams — use Physics signs. If it’s Chemistry-flavoured — reactions, enthalpy, bond energies — use Chemistry signs.

Write both forms at the top of your thermodynamics practice sheet. Making effective condensed notes matters here more than almost anywhere, precisely because of this clash.

Thermodynamics for NEET 2027: The Physics Side

Physics leans on the mechanical and gas-law aspects.

• The four processes. Isothermal (constant temperature), adiabatic (no heat exchange), isobaric (constant pressure) and isochoric (constant volume). Know what stays constant and what the first law reduces to in each.
• PV diagrams. Work done is the area under the curve. This is asked graphically almost every year.
• Heat engines and efficiency. The Carnot engine and its efficiency formula, and why 100% efficiency is impossible.
• Specific heats. Cp and Cv, and the relationship Cp − Cv = R for an ideal gas.

The thermodynamics physics NEET questions are mostly numerical, and PV-diagram work problems reward practice more than theory.

Thermodynamics for NEET 2027: The Chemistry Side

Chemistry leans on energy changes in reactions.

• Enthalpy. ΔH for reactions, and the sign difference between exothermic (negative) and endothermic (positive).
• Hess’s law. Enthalpy is a state function, so the total enthalpy change is independent of the path — the basis of most calculation questions, as solving previous year papers from both subjects quickly shows.
• Enthalpies of formation, combustion and bond enthalpy. Know how to combine them.
• Entropy and spontaneity. Entropy increases in spontaneous processes, and the second law.
• Gibbs free energy. ΔG = ΔH − TΔS, and the rule that ΔG negative means spontaneous. Gibbs free energy NEET questions lean on this more than any other, making it the highest-yield single equation in the Chemistry half.

The thermodynamics chemistry NEET questions are a mix of Hess’s law calculations and conceptual spontaneity questions built around Gibbs free energy.

The Concept That Ties Both Together

Spontaneity is where the two halves genuinely meet, and it’s worth understanding rather than memorising.

A process is spontaneous when Gibbs free energy decreases — when ΔG is negative. That single rule absorbs enthalpy, entropy and temperature into one criterion. An exothermic reaction isn’t automatically spontaneous; a reaction with increasing entropy isn’t automatically spontaneous. It’s the combination, weighted by temperature, that decides.

Understand ΔG = ΔH − TΔS properly and you can answer spontaneity questions from either subject’s framing. The sign logic fades fast without practice, so keep drilling it.

The Traps

• The sign convention clash. Physics ΔU = Q − W, Chemistry ΔU = Q + W. The number-one error.
• Assuming exothermic means spontaneous. It doesn’t — check ΔG.
• State function vs path function. Internal energy, enthalpy and entropy are state functions; heat and work are not.
• Adiabatic vs isothermal confusion. No heat exchange versus constant temperature — different constraints.
• Cp − Cv = R applying to ideal gases specifically.
• Sign of ΔG. Negative for spontaneous, and students reverse it under pressure.
• Forgetting temperature’s role in the Gibbs equation when it flips spontaneity.

Most of these are convention and sign errors rather than conceptual gaps, which is exactly why the overlap approach helps — learn the concept once, apply the right signs per subject.

How to Study It

1. Learn the shared core first — laws, state functions, the four processes, the key quantities. One study block, both subjects.
2. Then split for the specifics — PV diagrams and engines for Physics, Hess’s law and Gibbs energy for Chemistry.
3. Drill the sign conventions until you automatically know which subject you’re in.
4. Practise both question styles from Physics and Chemistry to see how differently the same laws get asked.

Budget slightly more than a single chapter, since you’re covering two — but far less than treating them as unrelated.

Thermodynamics for NEET 2027 is the clearest example in the whole syllabus of two chapters that are secretly one. Students who study them separately do double the work and still get tripped by the sign clash. Students who see the overlap learn the core once, split only for the specifics, and handle both papers’ framing confidently.

Learn the laws once. Keep the two sign conventions straight. Master ΔG = ΔH − TΔS. That covers most of what either subject will ask.