OCR 21st Century GCSE Chemistry required practicals: A complete guide

If you're on OCR Twenty First Century Chemistry B (spec code J258), there are 8 compulsory Practical Activity Groups you need to know. OCR calls them "PAGs" rather than required practicals: each PAG is a group of techniques, and your school picks one specific activity (or devises its own) that covers the apparatus and skills listed.

This guide walks through all 8 OCR B Chemistry PAGs in the specification's own order, explains how they're examined across the Breadth and Depth papers, and sets out the three important ways OCR B differs from OCR Gateway Chemistry A (J248). Different boards use different language for the same idea: OCR says "PAGs", AQA says "required practicals", Edexcel says "core practicals". This article is OCR Twenty First Century (OCR B) only.

The OCR specification states that learners must complete at least eight practical activities, which OCR has split into eight Practical Activity Groups (PAGs) based on Department for Education GCSE subject content requirements. OCR B labels its PAGs PAG1 to PAG8. Gateway separate Chemistry (J248) refers to the same groups as PAG C1 to PAG C8, so letter-prefixed codes are not unique to Combined Science. At Higher tier the papers are J258/03 (Breadth) and J258/04 (Depth), each 1 hour 45 minutes, 90 marks, 50% of the qualification.

Because each PAG is a group of techniques rather than a prescribed experiment, two schools can teach PAG 8 using different reactions (hydrochloric acid with marble chips, or sodium thiosulfate with hydrochloric acid) and both are valid. OCR publishes example activities but centres can substitute.

There's no separate practical exam for OCR B Chemistry. Practical skills are examined through written questions on both the Breadth and Depth papers, and your school signs a Practical Science Statement confirming you've completed the PAGs. The OCR specification states: "No less than 15% of the questions will assess practical skills." AO1 (demonstrate knowledge and understanding) and AO2 (apply knowledge and understanding) each account for 40% of the overall grade; AO3 (analyse information and ideas; interpret and evaluate; develop and improve experimental procedures) accounts for 20%.

Chemistry carries a mathematics floor of 20% across the papers (set by Ofqual at Level 2 Chemistry): a fifth of the marks need to involve calculation, formula rearrangement or data analysis. Several PAGs lean into that, PAG 6 Titration most obviously, where you'll be expected to calculate concentration using moles equals concentration times volume, and PAG 8 Measuring rates, where you'll be interpreting gradient and reading off tangents.

OCR B also runs an entire chapter called C7 "Ideas about Science" on separate J258. It isn't a PAG, but it covers scientific method, data interpretation and ethics, often framed around real-world contexts. Many of the Depth-paper extended-response questions sit at the intersection of a PAG and C7.

The practical-skills chapter on OCR B separate Chemistry is Chapter C8.

OCR Twenty First Century Chemistry B differs from OCR Gateway Chemistry A on three axes.

PAG labelling. OCR B separate Chemistry (J258) labels its 8 PAGs PAG1 to PAG8; OCR Gateway separate Chemistry A (J248) labels the same 8 groups PAG C1 to PAG C8. The PAG titles overlap closely (reactivity trend, electrolysis, separation techniques, distillation, identification of species, titration, production of salts, measuring rates of reaction). If a resource shows just five C-prefixed PAGs, that's a Combined Science list, not a separate-Chemistry list.

Paper structure. Gateway separate Chemistry (J248) splits content between papers; OCR B uses Breadth and Depth: both papers cover all chapters, differentiated only by question style. Breadth is multi-topic shorter questions; Depth is deeper application and extended-response synoptic reasoning. Don't go into the exam expecting "Paper 1 covers topics X to Y" on OCR B.

Chapter names. OCR B chapters use narrative-led titles: C1 Air and water, C2 Chemical patterns, C3 Chemicals of the natural environment, C4 Material choices, C5 Chemical analysis, C6 Making useful chemicals, C7 Ideas about Science, C8 Practical skills. Gateway uses more conventional labels. Swapping chapter labels between the two courses is a common revision slip.

Reading through the method isn't enough. PAGs test whether you can think like a scientist, not whether you can recite a recipe.

For each PAG, pick the activity your class ran and write the method out from memory. Then check it against your notes or a Cognito video. The steps you forgot are the ones that would have cost you marks. Pay attention to the small details OCR likes to probe: using a pipette and a volumetric flask for concentration work in PAG 6, reading a burette at eye level with the meniscus on the line, calculating R_f as substance distance over solvent distance in PAG 3, running flame tests with a clean nichrome wire dipped in concentrated hydrochloric acid between tests in PAG 5.

For each PAG, prepare answers for the four question types that keep coming up: method, variables, explanation of results, evaluation and improvement. A specific improvement with a specific reason, not "repeat it".

Sketch the graphs you'd expect for the quantitative PAGs. For PAG 8 Measuring rates, a curve that rises (gas volume) or falls (mass of reaction flask) over time, with the initial gradient steepest and the plateau representing complete reaction. For PAG 6 Titration, a sharp pH jump near the equivalence point when you plot pH against volume added. For PAG 2 Electrolysis, a labelled diagram of the circuit with correct symbols for the electrodes and electrolyte.

For the Depth paper, practise linking a PAG to C7 Ideas about Science reasoning. A question on PAG 1 (reactivity trend) can swerve into evaluating whether a conclusion is justified given variability in the data, or whether a model (e.g. electron configuration) explains an observed pattern. Our guide to getting a grade 9 in GCSE Chemistry walks through these synoptic patterns and other exam techniques worth practising.

Work through past paper questions by PAG. OCR recycles wording and graph shapes year on year, and the mark schemes are the clearest guide to the exact phrases they want.

Our OCR Twenty First Century Chemistry course covers all 8 PAGs through short video lessons, worked examples and exam-style questions. Each PAG has its own lesson walking through the technique, apparatus, variables and exam language. Jump into the OCR B Chemistry course and track your progress through the whole spec. For the wider shape of the qualification, our complete guide to OCR Twenty First Century GCSE Chemistry covers Breadth and Depth paper structure, chapter list and timing in one place.