Common G3 Chemistry exam mistakes

Most lost marks in G3 Chemistry aren't from not knowing the chemistry — they're from avoidable slips: dropped units, misread command words, sloppy structural formulae and rushed calculations. Here are the ones that come up most, and how to stop them.

Units and significant figures

K324 penalises misused units and significant figures, so a correct number with the wrong unit still drops the mark. Carry units through every line of a calculation, convert cm³ to dm³ when needed, and match the precision of the data. This single habit recovers more marks than any extra topic revision.

Misreading command words

“State” wants a concise answer with no argument; “explain” needs reasoning or theory; “predict” or “deduce” means follow the logic with no recall required. Answering an “explain” with a one-word “state” answer is a frequent, needless loss. Read the command word first and shape the answer to it.

Structural formulae and conventions

Full structural formulae must show every atom and bond — condensed forms like –CO₂H are not accepted as full structures. Spell sulfur with an f throughout (sulfate, sulfite), and use dm³ rather than litre. These conventions are expected, and ignoring them costs easy marks.

Qualitative analysis mix-ups

QA marks are lost by confusing similar results — for instance, which hydroxide precipitates redissolve in excess. Work from the printed notes methodically and record exactly what you see (colour, precipitate, gas) before deducing the ion, rather than guessing the ion and forcing the observation.

The data-based question

New in K324, Section A of Paper 2 ends with a data-based question worth 8–12 marks. Students lose marks by describing the data instead of using it — read what's actually asked, refer to specific values, and draw the conclusion the data supports. Practise this question type specifically; it rewards a calm, evidence-led answer.