NOTES · SUBJECT CHOICE
Pure or combined science: what Combined Science is and how the papers differ
Method & Mark · · updated
Combined Science is one subject made of two of the three sciences: Physics and Chemistry, Physics and Biology, or Chemistry and Biology. It is examined as one subject and gives one grade. Students sitting the O-Level in 2026 take it as syllabus 5086, 5087 or 5088. From 2027, under the Singapore-Cambridge Secondary Education Certificate (SEC), the same three combinations are G3 subjects K326, K327 and K328. The alternative, chosen from Sec 3, is to take sciences as pure subjects, such as Physics (K323) and Chemistry (K324), each a full G3 subject with its own three papers and its own grade. This note explains what Combined Science is, then compares it with the pure sciences in three places: how the papers are built, how much is examined, and how the grades count for junior college.
What Combined Science is
SEAB lists Combined Science under the title Science, with the two sciences in brackets. There are three combinations, and each has its own syllabus code:
| Subject | O-Level 2026 | SEC from 2027 |
|---|---|---|
| Science (Physics, Chemistry) | 5086 | K326 |
| Science (Physics, Biology) | 5087 | K327 |
| Science (Chemistry, Biology) | 5088 | K328 |
The 2027 SEC syllabus is a single document for all three codes. It has a Physics section, a Chemistry section and a Biology section, and each combination is examined on two of them. Every candidate sits four papers:
- Paper 1
- 40 multiple-choice questions in 1 h, covering the two sciences in roughly equal parts. 20% of the grade.
- Papers 2, 3, 4
- One structured paper per science: Paper 2 Physics, Paper 3 Chemistry, Paper 4 Biology. Each is 1 h 15 min for 65 marks and 32.5% of the grade. Section A is 55 marks of compulsory questions. Section B is 10 marks, answering one of two questions.
- Paper 5
- A practical test of 1 h 30 min for 30 marks, with one or two questions on each science. 15% of the grade.
Papers 1 and 5 are set at the same time for all three codes, and the practical questions on each science are shared between the combinations that include it. In the practical, the only reference material allowed is the Chemistry Practical Notes printed in the syllabus, the same qualitative analysis tests that Pure Chemistry students learn.
Whichever two sciences it contains, Combined Science is one subject. It has one code on the timetable and one grade on the certificate, and for junior college admission it fills one subject slot, not two.
How much of the grade each science carries
Because the two sciences share Papers 1 and 5, neither has a grade of its own. Working out the chemistry share of a K326 grade from the weightings:
The halves are approximate: SEAB says Paper 1 covers the two sciences in roughly equal parts, and does not fix how the practical’s marks split. Still, the result is the point. In Combined Science, chemistry is about half of one grade. In Pure Chemistry, it is the whole of its own grade. A strong chemistry half can lift a weaker physics half, and the reverse is also true.
Pure against combined: the papers
| Paper | Pure Physics or Chemistry | Science (Phy, Chem) |
|---|---|---|
| Multiple choice | 1 h · 40 marks · 30% | 1 h · 40 marks · 20%, both sciences |
| Structured | 1 h 45 min · 80 marks · 50% | Two papers, one per science: 1 h 15 min · 65 marks · 32.5% each |
| Practical | 1 h 50 min · 40 marks · 20% | 1 h 30 min · 30 marks · 15%, both sciences |
Taking Pure Physics and Pure Chemistry means six papers and two grades. Combined Science is four papers and one grade.
What the pure syllabuses add
The chemistry half of Combined Science has the same twelve topic headings as Pure Chemistry, covered in less depth. The physics half has sixteen topics to Pure Physics’ twenty. Some of what only the pure syllabuses examine:
- Pure Physics
- Electromagnetic induction, including transformers and a.c. generators. Specific heat capacity and latent heat.
- Pure Chemistry
- Electrolysis, transition elements, and esters and more depth in organic chemistry.
This matters most for students heading to H2 Physics or H2 Chemistry in JC, where these topics are built on.
How the grades count for junior college
From the 2028 admissions exercise, JC admission uses an L1R4 score: English or Higher Mother Tongue plus four relevant G3 subjects. Pure Physics and Pure Chemistry are two separate subjects, so both can count. Combined Science is one subject and gives one grade. One of the four relevant subjects must be a mathematics or science subject.
Students sitting the O-Level in 2026 apply in the 2027 JAE, which still uses L1R5. There, too, Combined Science is one subject and one grade. O-Level results 2026 works through how L1R5 and L1R4 are counted.
Junior colleges can also set their own subject requirements for H2 sciences. Check the admission pages of the JCs your child is considering.
Questions to ask before choosing
- Is H2 Physics or H2 Chemistry likely in JC? The pure syllabuses cover more of what those subjects assume.
- How is the current science grade? Pure sciences mean more content and six papers, with each grade carrying its own weight in L1R4.
- What does the school offer? Schools decide which combinations they run and how students are placed, so ask early.
Sources
SEAB, 2027 SEC G3 syllabuses for school candidates: Physics K323, Chemistry K324, and Science K326, K327 and K328. SEAB, 2026 GCE O-Level syllabuses examined for school candidates: Science 5086, 5087 and 5088. MOE, JC and MI admission criteria from the 2028 PSE. Check these pages before deciding, as details can change.
How we teach it
We teach maths: Additional Mathematics and Mathematics (E Math) for Sec 3 and Sec 4, in classes of five, marked against the scheme. Start with a trial class.