IGCSE Combined Science vs Separate Chemistry
The differences between Cambridge IGCSE Combined Science and separate IGCSE Chemistry 0620. Content, grades and implications for further study.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
The choice between Combined Science and separate IGCSE Chemistry affects how much chemistry your child learns, what grade they can achieve, and what doors open at A-Level or IB. This guide breaks down the differences clearly.
What each qualification covers
Separate IGCSE Chemistry (0620)
A full, standalone qualification covering all 12 topics of the chemistry syllabus in depth. Students sit three papers (MCQ, theory and alternative to practical) and receive a single grade on the A* to G scale (Extended candidates can reach A* to G; Core candidates C to G).
Combined Science (0653)
A single qualification covering biology, chemistry and physics in less depth than any of the three separate sciences. The chemistry portion typically covers around 60-70% of the separate IGCSE Chemistry syllabus. Students sit papers that include questions from all three sciences and receive one or two grades.
Content differences
The topics covered in both qualifications overlap, but Combined Science trims the depth:
| Topic | Separate Chemistry (0620) | Combined Science (0653) |
|---|---|---|
| Atomic structure | Full detail including electronic configuration | Core concepts, less detail |
| Stoichiometry | Mole calculations, empirical formula, concentration, percentage yield | Basic mole calculations |
| Organic chemistry | Four homologous series, reactions, polymers, isomerism | Fewer series, less reaction detail |
| Electrochemistry | Electrolysis, half-equations, simple cells, fuel cells | Basic electrolysis |
| Energetics | Bond energy calculations (Extended) | Exothermic/endothermic classification |
| Rates and equilibrium | Collision theory, equilibrium shifts (Extended) | Basic rate factors |
The effect is cumulative: a student taking Combined Science encounters the same concepts but practises them less and at a lower level of complexity.
Grading and university recognition
IGCSE Chemistry
Graded A* to G (Extended candidates can reach the full A* to G range; Core candidates C to G). This is a standalone qualification listed separately on certificates and university application forms.
Combined Science
Graded as a single subject or double award. The chemistry component does not receive a separate grade. Universities and sixth forms see “Combined Science” on the certificate, not “Chemistry.”
For university applications:
- Most universities accept Combined Science as meeting science requirements at GCSE/IGCSE level.
- Competitive science courses (medicine, engineering, natural sciences) at top universities often prefer or require separate sciences.
- A-Level chemistry programmes may require a higher grade in Combined Science for entry than they would for separate Chemistry.
Implications for A-Level Chemistry
This is the most important consideration for many families.
Coming from separate IGCSE Chemistry
Students arrive at A-Level having covered the full syllabus. They have practised mole calculations extensively, written many equations, and studied organic chemistry in detail. The transition to A-Level builds on solid foundations.
Coming from Combined Science
Students arrive at A-Level with gaps in content and less practice with complex questions. Common areas where they struggle:
- Mole calculations beyond the basics.
- Organic chemistry reactions and mechanisms.
- Electrochemistry detail.
- Extended-style explain questions.
These gaps are closable, but they require extra work in the first months of A-Level. Some schools provide a bridging course; others expect students to close the gaps independently.
More on the IGCSE to A-Level transition is in IGCSE Chemistry to A-Level.
Which to choose
Choose separate IGCSE Chemistry if:
- Your child enjoys chemistry or science generally.
- They might study chemistry, biology or a related subject at A-Level or IB.
- They are aiming for competitive university courses in science or medicine.
- The school offers it and the timetable allows it.
- Your child can manage the workload of three separate sciences.
Choose Combined Science if:
- Your child does not plan to study any science at A-Level.
- The timetable does not accommodate three separate sciences alongside other subject choices.
- Your child finds science challenging and would benefit from a less intensive course.
- Your child needs more time for subjects that are higher priority for their future plans.
The middle ground
Some schools allow students to take separate Chemistry alongside Combined Science for biology and physics (or any other combination). This gives full Chemistry preparation while reducing the overall science workload. Check whether your school offers this flexibility.
If you are already in Combined Science and considering switching
A mid-course switch from Combined to separate Chemistry is possible but requires:
- Learning the additional content not covered in Combined Science.
- Practising the separate Chemistry exam format (Paper 6, Extended MCQ).
- Getting up to speed on the depth expected in theory answers.
The switch is easier in Year 10 than in Year 11. If your child is considering it, the sooner the better. A trial lesson can assess where they stand and how much additional work the switch would require.