Physical chemistry sits between Physics and Chemistry and inherits the difficulties of both: the conceptual load of one, the arithmetic of the other. The marks are usually lost to the arithmetic.
A formula without its conditions is a trap
Nearly every relationship you will use holds under stated conditions — constant temperature, ideal behaviour, a particular reaction order. A formula memorised without them will eventually be applied where it does not hold, and the answer will look reasonable.
When you write a formula in your notes, write the conditions on the same line. Not underneath, not on the next page.
Units are where the marks go
The gas constant alone appears with several different units depending on what you are computing. Choosing the wrong one gives an answer wrong by a clean factor — which is exactly the kind of wrong that matches a distractor.
Write units at every step. Not at the end.
The topics that reward a method
- Mole concept — underneath more questions than its own chapter. Weak here means weak across stoichiometry, solutions and electrochemistry at once.
- Equilibrium — set up an ICE table every time, even when it seems unnecessary. The discipline prevents the error.
- Thermodynamics — sign conventions decide the answer, and they are the thing most often got wrong under pressure.
- Kinetics — identify the order first; the rest follows from it mechanically.
Build one formula sheet, by hand
Not printed, not downloaded. Writing it is the revision; the sheet is a by-product. Organise by topic, with conditions and units beside each entry, and rebuild it from memory every few weeks.
What you cannot rebuild is what you have not learned — which is more useful to discover in March than in the hall.
Estimate before you compute
A rough order-of-magnitude expectation costs seconds and catches the decimal-place error, which is the most common arithmetic mistake in this section and the hardest to spot by rereading.