OCR runs two GCSE science suites. Gateway Science is Chemistry A, J248, which is this guide. Twenty First Century Science is Chemistry B, J258 and is organised completely differently.

The code is on your exam timetable. Gateway chemistry topics are numbered C1 to C6.

This is the Higher tier guide, offering grades 9 to 4, with an allowed 3.

At OCR the tier also changes the paper number. Foundation sits Papers 1 and 2 and Higher sits Papers 3 and 4. You are sitting Paper 3 and Paper 4.

Higher carries everything on the Foundation papers plus the higher-tier content, so a student later moved to Foundation has lost nothing.

Then you need a different guide. Combined Science A is J250, a double award worth two GCSEs, and it examines less chemistry than the separate Chemistry A. Working from this guide would mean learning content your papers will not ask for.

The one you want is OCR GCSE Combined Science Chemistry, Higher.

Paper 3 covers Chemical Reactions, Elements, Compounds and Mixtures, Particles. Paper 4 covers Global Challenges, Monitoring and Controlling Chemical Reactions, Predicting and Identifying Reactions.

The second paper assumes the content of the first, so nothing from the first half is ever safely dropped. The full breakdown is here.

Yes, and they sit in the topics they belong to rather than being folded into theory: relative formula mass, the mole and the Avogadro constant, conservation of mass, reacting masses, empirical formulae, concentration, percentage yield, atom economy and Rf values.

OCR examines practical work on the written papers rather than in a separate component, so the techniques sit inside the topics they belong to: titration, chromatography and Rf values, making a soluble salt, electrolysis, rates of reaction, temperature change in reactions, and the tests for ions and gases.

By subtopic, never by topic. The largest topic here is 353 questions, which is not a session. It divides into subtopics of 8 to 25 questions, and one of those is twenty minutes.

Any point in Year 10 or Year 11. Both papers are sat at the end of Year 11 and cover the full two years, so no part of the guide is too early.

The usual pattern is a subtopic in the week it is taught, then returns on days 1, 3, 7, 14 and 30.

Yes. This guide handles recall. Past papers handle the six-mark answers, the unfamiliar contexts and finishing the paper in the time. OCR publishes them free.

A PDF of 1,265 exam-style questions covering the whole of OCR GCSE Chemistry A, Higher tier, with the answers printed after each topic.

It is not a textbook. It is the tool for getting taught content into memory and for showing whether it went in.

Three things decide it, and all three are on the exam timetable.

The suite. OCR Gateway is Chemistry A, J248. Twenty First Century is Chemistry B, J258.
The route. Separate sciences, sat as three GCSEs, are not the same as Combined Science, a double award covering all three.
The tier. Higher offers grades 9 to 4, with an allowed 3, and at OCR the tier changes the paper numbers.

This is the separate science GCSE, Chemistry A (J248), one of three sat alongside the other two sciences. This guide is the Higher tier, sitting Paper 3 and Paper 4.

There should be handwritten answers on paper and three passes over the same questions. The method produces two numbers each session, the score on the first closed-book pass and the score on the third. Those two numbers are a better thing to ask for than the number of hours spent.

Rereading and highlighting are the two most common revision activities and Dunlosky and colleagues rated both low utility in their 2013 review of ten techniques. They raise how familiar the material feels without raising the ability to produce it with the book shut.

The method page sets out what to do instead.

£7.00 for the whole specification at that tier. A GCSE chemistry revision guide is usually £6 to £10 and a full textbook £20 to £30. The three separate sciences are sold as three guides because they are three qualifications with three sets of papers.

82 subtopics at roughly twenty minutes each is about 27 hours for a full first pass of the course. Returns afterwards are three to five minutes each.

That is your school’s decision and they will make it on mock performance. What is worth knowing is that Higher offers grades 9 to 4, with an allowed 3 and Foundation caps at grade 5.

Higher content is a superset of Foundation content, so a student preparing on this guide who is later moved to Foundation has lost nothing.

Past papers, free from OCR, a calculator, and their own notes for anything not yet taught.