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GCSE chemistry explained
Whether your child is taking Combined Science or the separate sciences, what that actually changes, and how the boards differ. Everything here comes from the exam boards' own documents.
Combined Science or separate chemistry?
This is the decision that shapes GCSE chemistry, and it is usually made by the school rather than by the family, somewhere around Year 9.
Combined Science covers biology, chemistry and physics in one course and is worth two GCSEs. Separate sciences, which schools often call triple science, are three GCSEs with more content in each. In many schools both are taught in the same lessons for a while before the classes split.
Neither route closes a door. A student who takes Combined Science can go on to A Level chemistry. Sixth forms set their own entry grades, and those are worth asking about directly rather than assuming.
What Combined Science leaves out of chemistry
We went through the AQA specification topic by topic. Of the 68 topics in our GCSE chemistry list, 52 are taught to everyone, 2 are taught to everyone but with some of the detail removed, and 14 appear only in the separate GCSE.
Only in separate chemistry — 14 of 68
- Transition metals — Atomic structure and the periodic table
- Nanoparticles — Bonding, structure and properties of matter
- Percentage yield — Quantitative chemistry
- Atom economy — Quantitative chemistry
- Gas volumes — Quantitative chemistry
- Alkenes — Organic chemistry
- Alcohols, carboxylic acids and esters — Organic chemistry
- Addition and condensation polymers — Organic chemistry
- Natural polymers — Organic chemistry
- Flame tests and metal hydroxides — Chemical analysis
- Tests for anions — Chemical analysis
- Instrumental methods — Chemical analysis
- Corrosion and rusting — Using resources
- Alloys and composites — Using resources
Taught to both, but cut down for Combined Science — 2 of 68
These topics are on both courses. A Combined Science student meets them with part of the content taken out.
- The pH scale and strong versus weak acids — Chemical changes
- Bond energy calculations — Energy changes
This split is AQA’s. Our topic list follows AQA’s structure, and the other boards draw the line in slightly different places. If your child’s school uses Edexcel or OCR the overall shape is similar but the details are not identical, and the school can tell you exactly what is being taught.
How it is graded
Separate chemistry is a GCSE in its own right, graded 9 down to 1, with 9 the highest.
Combined Science is reported differently. It is a single award worth two GCSEs, and it comes out as a pair of grades rather than one — 9–9, 9–8, 8–8 and so on down to 1–1, seventeen outcomes in all. The two numbers are always either the same or one apart, and the higher is written first. It is not two separate subject results: the whole mark total across every paper decides which pair a student gets.
Both routes are sat at Foundation or Higher tier, and every paper is sat at the same tier. Foundation reaches a grade 5, or 5–5 on Combined Science. Higher starts at grade 4 and reaches 9, or 9–9.
The exam boards
Four boards offer GCSE sciences in England, but there are five Combined Science qualifications, because AQA and OCR each offer two. “We do OCR” is not quite enough to go on — the two OCR courses are examined quite differently from one another.
| Combined Science | Code | Papers | Marks | Practicals |
|---|---|---|---|---|
| AQA Combined Science: Trilogy | 8464 | 6 | 420 | 21 |
| AQA Combined Science: Synergy | 8465 | 4 | 400 | 21 |
| Edexcel Combined Science | 1SC0 | 6 | 360 | 18 |
| OCR Combined Science A (Gateway Science) | J250 | 6 | 360 | 16 |
| OCR Combined Science B (Twenty First Century Science) | J260 | 4 | 360 | 16 |
And for separate chemistry:
| Board | Code | Papers | Marks | Practicals |
|---|---|---|---|---|
| AQA | 8462 | 2 | 200 | 8 |
| Edexcel (Pearson) | 1CH0 | 2 | 200 | 8 |
| OCR Gateway Science A | J248 | 2 | 180 | 8 |
| OCR Twenty First Century Science B | J258 | 2 | 180 | 8 |
The practicals column is not measuring quite the same thing in every row. AQA and Edexcel name the experiments that have to be done. OCR does not: it sets out groups of skills and asks schools to cover them with at least that many activities, which the school can choose or design itself. Every board assesses practical work through the written papers rather than separately, and at least 15 per cent of the marks go on it.
Eduqas is not in the tables. Its GCSE Combined Science was withdrawn and is listed as archived on the Department for Education’s register of funded qualifications. Eduqas is still a live board for GCSE maths, so a school using Eduqas for maths is not necessarily using it for science.
What this page cannot tell you
No board publishes how much of a chemistry paper comes from each topic. For GCSE maths they do, and our maths guide sets those weightings out. For the sciences the figures do not exist, so a percentage breakdown of a science paper is somebody’s estimate rather than the board’s.
Everything above comes from the exam boards’ own specifications, read in September 2026. Specifications are revised from time to time. If a detail here matters to a decision, the school’s own copy is the thing to check.