CSIR-NET Chemical Sciences Part C: How Physical Chemistry Is Really Asked

The structural difference nobody explains early enough

Chemical Sciences is set in three parts. Part A is general aptitude, common across CSIR subjects. Part B tests subject fundamentals in a fairly direct way. Part C is where the marks per question rise and the question style changes character entirely.

The change is not difficulty in the sense of heavier algebra. It is that a Part C question typically does not tell you which topic it belongs to. You are given a situation — a reaction under stated conditions, a spectrum, a plot, a set of thermodynamic data — and the first real task is identifying which principle governs it. Candidates who have revised topic by topic, and who expect questions to arrive labelled by topic, find this disorienting.

What Part C physical chemistry tends to demand

Cross-topic questions are the real Part C signature

A single Part C question will often sit across two units at once. A kinetics question may require an equilibrium constant obtained thermodynamically. A spectroscopy question may need a symmetry argument to decide whether a mode is active. A question on electrode potential may hinge on a solubility product.

The practical consequence for revision is direct: studying units in isolation and never mixing them leaves a real gap. Once you have covered thermodynamics and kinetics separately, deliberately practise questions that need both, because the paper will not keep them apart.

Negative marking changes what a good attempt looks like

Because incorrect answers are penalised, raw attempt count is not the objective. What matters is expected marks. A question you can narrow to two options is often worth attempting; one where all four remain plausible usually is not.

• First pass: answer only what you recognise and can finish quickly. Do not linger.
• Second pass: return to questions where you can eliminate at least two options on sound reasoning.
• Leave alone: questions where elimination is guesswork dressed up as reasoning. This is a discipline, and it has to be practised under timed conditions or it collapses on the day.

How to prepare differently for Part C

Work backwards from previous papers

Solve previous-year questions not for the answer but to categorise the reasoning step each one demanded. Patterns emerge quickly: certain topics are asked overwhelmingly as derivation-adjacent reasoning, others almost always as numericals.

Learn derivations to the point of adaptability

Part C rarely asks you to reproduce a derivation. It asks what happens when one assumption in that derivation is changed. That is only answerable if you know which step each assumption entered at.

Keep a running error log

Record every wrong answer with the reason it was wrong — concept gap, misread question, arithmetic, or wrong topic identified. Most candidates find one category dominates, and fixing it is worth more than another textbook.

Frequently asked questions

Is Part C harder than Part B?

Different rather than uniformly harder. Part C questions carry more marks and more often demand multi-step reasoning, but a well-prepared candidate frequently finds some Part C questions more approachable than obscure Part B recall.

How much of the syllabus does Part C actually draw on?

In principle the whole syllabus. In practice certain units recur heavily, which previous papers reveal clearly — but building a preparation plan that ignores the rest is a gamble, since weighting shifts between sessions.

Should I attempt every question I am allowed to?

No. With negative marking, the correct target is maximum expected marks, not maximum attempts. Attempting a question you cannot narrow down has negative expected value.

Does Part A really matter?

Yes, and it is the most commonly neglected section. It is scoring, it is learnable in far less time than any subject unit, and candidates regularly lose qualification on it after preparing chemistry thoroughly.