Where the marks actually go
Organic chemistry is the single biggest topic in this subject, worth close to a sixth of the whole qualification on its own. Metals and the reactivity series, quantitative chemistry in Unit 2, bonding and the Periodic Table make up most of the rest, with the practical skills unit adding its own thirty-plus marks for how well you can carry out and record an experiment. If your revision time is limited, organic chemistry and quantitative chemistry are where an extra hour pays back the most.
The recurring pattern in examiner reports is not missing knowledge, it is missing precision: dropped state symbols, electrons placed on the wrong side of a half-equation, titration scale-ups forgotten, and rate of reaction explanations that describe a change without saying why it happens. Every one of these is fixable without learning a single new fact.
Paper structure and timing
Unit 1 is 75 minutes for 80 marks across five questions, so roughly 15 minutes a question, weighted towards the ones carrying more marks. Unit 2 is 90 minutes for 100 marks across six questions, close to a minute a mark. Both units carry one 6-mark extended response marked for quality of written communication. Spot that question early in each paper and plan to write it in full sentences rather than a list of points.
Unit 3 is the practical skills unit, split into two booklets. Booklet A is the hands-on lab paper: two hours for 30 marks, recording observations, pH results and temperature data directly into the tables provided. There is no reward for finishing early here, only for recording data cleanly and consistently. Booklet B is 60 minutes for 70 marks across five questions covering halogen identification, gas volume calculations, apparatus diagrams and solubility graphs, so around 12 minutes a question.
Where the technique pays off
Structured short-answer and calculation questions carry the largest share of marks across both theory units, with equations and half-equations close behind. A few habits consistently separate strong scripts from average ones.
- Say why the rate changed, not just that it did. 'The rate increases' on its own earns little. Say that increasing concentration increases the frequency of collisions per unit time, or the equivalent for temperature or surface area.
- Balance electrons on the correct side. In electrolysis half-equations, check which side the electrons belong on before you submit an answer, for example 2Cl- minus 2e- gives Cl2, not the reverse.
- Scale titration results all the way through. If a 25 cm3 sample came from a 250 cm3 volumetric flask, multiply your final answer by 10 before you finish. This single scaling step is one of the most common places a correct calculation still loses its final mark.
CCEA conventions to know
Both theory units carry one 6-mark QWC question, marked against a banded mark scheme with a minimum mark threshold for each band. Reaching the top band means covering the required scientific content in continuous prose with correct spelling, punctuation and grammar, not writing more.
State symbols are only needed when a question specifically asks for them, but when it does, every species needs one, including (aq) for ions in solution and (l) for water. Missing one state symbol in an otherwise correct equation is a common one-mark loss.
The week before
Redo a full set of titration and empirical formula calculations end to end, including the scaling step from sample volume back to the full volumetric flask. Write out electrolysis half-equations for at least three different electrolytes, checking the electron balance each time. Practise a 6-mark QWC answer to a strict timed limit so covering every indicative content point becomes automatic. On the day, read every calculation question twice before starting: once for what is being asked, once to check what units and precision the final answer line requires.