Most students think of checking as reading their answers back once at the end, nodding, and hoping. That kind of check catches almost nothing, because your eye simply re-reads what your brain already expects to see. Real checking is an active, structured hunt for specific mistakes you know you tend to make. Done well, it is one of the highest-value habits in the whole exam, the marks you rescue in the last ten minutes cost you no new chemistry at all. Here is how to check properly.
Leave time to check, and plan for it
You cannot check answers you have not left time for. Before the exam, decide how the clock will run: aim to finish the writing with a real margin, not on the final bell. In Paper 2, a rough target of a mark a minute leaves you a genuine cushion at the end. Treat the last stretch as a fixed, non-negotiable checking phase, not as spare time you will only use “if there is any”. The plan is what makes the check happen.
Check against how the paper is marked
Examiners award marks for specific things, so check for those specific things rather than a vague “does this look right”. If you know how SPM Chemistry is marked, you know where the easy marks hide: a state symbol, a unit, a correctly balanced equation, the right command-word response. Run a targeted pass looking only for those, one type at a time. Checking one category across the whole paper is far more effective than reading each answer once and trying to catch everything at once.
The careless-error checklist
Do separate sweeps, each hunting one kind of slip:
- Units. Every final numerical answer needs a unit:
mol,g, mol dm−3, cm3, dm3,kJ,°C. A right number with no unit is often marked wrong. - State symbols. In every equation, confirm
(s),(l),(g)and(aq)are present and correct. AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq), the(s)on the precipitate is a mark. - Balancing. Recount every equation, element by element, both sides. C2H5OH + 3O2 → 2CO2 + 3H2O balances; a quick recount catches a dropped coefficient.
- Significant figures. Give sensible final figures, usually three, and check you did not round midway.
- Charges and formulae. Confirm ionic charges and formulae: sulfate is SO42−, not SO4−; calcium chloride is CaCl2, not
CaCl. - Command words. Did an “explain” answer actually give a reason, not just a fact? Did a “compare” answer include both sides?
Back-substitute your calculations
The most reliable check for a calculation is to work it backwards or sanity-test the size of the answer. If you found that 0.1 mol of CaCO3 decomposes, its mass should be 0.1 × 100 = 10 g, put the number back into the mass–mole relationship and confirm it fits. Ask whether the answer is even plausible: a titration needing 2500 cm3 of acid, or a “mass” that comes out negative, is telling you something slipped. For method and layout that make back-checking easy, see our guide to calculation questions. A calculation you can retrace is a calculation you can trust.
Re−read what the question actually asked
A surprising share of lost marks come from answering a slightly different question than the one printed. Re−read the stem and underline the exact quantity or species asked for. Did it want the mass or the number of moles? The volume of gas at room conditions or at s.t.p.? The name of the product or its formula? Two decimal places or three? Students who “know the chemistry” still lose marks by giving a correct answer to the wrong question. Checking that your answer matches the question’s demand is quick and often decisive.
Watch the precise words
Chemistry is marked on exact vocabulary, so a check should include your wording. “Atom” is not “molecule”; “melting” is not “dissolving”; a “strong acid” (fully ionised) is not a “concentrated acid”. If a definition felt shaky as you wrote it, flag it and reconsider the term. When you are unsure of the precise word, our glossary has the mark-scheme wording, worth memorising for the terms you keep confusing.
Fill every blank before you check anything else
The very first thing to do when you reach the checking phase is scan for blanks. An unanswered question is a certain zero, and even a partial attempt can score. On the objective paper there is no penalty for a wrong choice, so never leave one empty, eliminate and commit. A blank is the one mistake that a good check should never allow to survive to the end of the exam.
Make checking a trained habit
None of this works if you invent it for the first time in the exam hall. Build the checklist into every past paper you sit, so that by SPM the sweeps are automatic and fast. If you would like a teacher to show you exactly which slips your own scripts keep leaking, our online one-to-one lessons do precisely that, taught in English, from RM50 an hour, with a paid one-hour trial. Checking is not glamorous, but it is where careful students quietly out-score clever ones.
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