G2 and G3 Combined Science in the 2027 SEC both offer three subject pairings, but they have different examination structures. G2 uses two papers for each selected science—one multiple-choice paper worth 20% and one structured paper worth 30%—so each science contributes 50%. G3 uses a shared multiple-choice paper worth 20%, two subject-specific structured papers worth 32.5% each, and a formal practical test worth 15%. In G3, the candidate takes Paper 1, Paper 5 and two of Papers 2, 3 and 4 according to the selected pairing.
The practical distinction is equally important. The G2 K223/K224/K225 scheme does not list a separate national practical paper, although students are expected to complete practical work and understand experimental techniques. G3 K326/K327/K328 includes Paper 5 Practical, a 1-hour-30-minute examination. A family moving from G2 to G3 Combined Science should therefore prepare for a different assessment contract, not assume that the same worksheets and laboratory routine will be sufficient.
SEC 2027: G2 versus G3 Combined Science at a glance
| Feature | G2 Combined Science | G3 Combined Science |
|---|---|---|
| Physics/Chemistry | K223 | K326 |
| Physics/Biology | K224 | K327 |
| Chemistry/Biology | K225 | K328 |
| Multiple-choice | Two subject-specific MCQ papers, each 20 marks and 20% | One combined Paper 1, 40 marks and 20% |
| Structured response | Two subject-specific papers, each 30 marks and 30% | Two selected subject-specific papers, each 65 marks and 32.5% |
| Practical | No separate national practical paper in the published scheme; practical learning is expected | Paper 5 Practical, 1 h 30 min, 30 marks, 15% |
| Candidate paper selection | Four of six possible papers: both papers for each selected science | Paper 1, Paper 5 and two of Papers 2, 3 and 4 |
| Assessment balance | Each science 50%: MCQ 20% + structured 30% | MCQ 20% + two structured papers 65% + practical 15% |
Official sources: SEAB’s 2027 G2 K223/K224/K225 syllabus and 2027 G3 K326/K327/K328 syllabus. The G2 and G3 codes are listed separately in SEAB’s G2 and G3 subject catalogues.
1. G2: the two sciences each have their own MCQ and structured paper
G2 uses a common numbering arrangement across three possible pairs. Papers 1 and 2 are Physics, Papers 3 and 4 are Chemistry, and Papers 5 and 6 are Biology. The candidate sits the two papers for each of the two sciences selected:
- K223 Physics/Chemistry: Papers 1, 2, 3 and 4.
- K224 Physics/Biology: Papers 1, 2, 5 and 6.
- K225 Chemistry/Biology: Papers 3, 4, 5 and 6.
The MCQ paper for each discipline is 20 marks and 20% of the overall subject. The structured paper for that same discipline is 30 marks and 30%. The relevant pair of papers is taken in one 1-hour-15-minute session, and the syllabus advises candidates not to spend more than 30 minutes on each MCQ component.
Because each science is weighted equally, a strong overall performance requires a workable balance. A learner who is confident in Chemistry but leaves Biology revision until the end is exposing half of the subject grade to avoidable risk. The better schedule identifies the first repeated error in both sciences, then allocates practice accordingly.
2. G3: one MCQ paper, two chosen structured papers and a formal practical
G3 Combined Science uses a different arrangement. Candidates enter for Paper 1, Paper 5 and two of Papers 2, 3 and 4. Paper 1 is a one-hour, 40-mark multiple-choice paper worth 20%. Papers 2, 3 and 4 are subject-specific structured/free-response papers, each 1 hour 15 minutes and 65 marks; the candidate sits the two relevant to the chosen pairing. Each contributes 32.5%. Paper 5 is the 1-hour-30-minute practical test, worth 30 marks and 15%.
The three G3 combinations map as follows:
| G3 code | Pairing | Subject-specific structured papers | Practical coverage |
|---|---|---|---|
| K326 | Physics/Chemistry | Paper 2 Physics + Paper 3 Chemistry | Physics and Chemistry |
| K327 | Physics/Biology | Paper 2 Physics + Paper 4 Biology | Physics and Biology |
| K328 | Chemistry/Biology | Paper 3 Chemistry + Paper 4 Biology | Chemistry and Biology |
Paper 1 covers the two disciplines in the selected pairing. Paper 5 also covers the relevant pair. In other words, G3 does not ask the candidate to sit all three subject-specific structured papers; the registered combination determines the two taken.
3. Why Paper 5 changes the G2-to-G3 transition
The G3 Paper 5 Practical is a formal national practical test. It assesses the candidate’s ability to carry out procedures, make observations or measurements, record results and use experimental evidence. The actual task depends on the two sciences in the registered pairing. Physics practical work may involve measurements and investigations; Chemistry and Biology have their own laboratory techniques and safety requirements.
At G2, the published scheme does not show a separate national practical paper. However, the G2 syllabus expects students to have carried out at least four practical tasks from the relevant lists and to be familiar with laboratory procedures. Practical techniques may be referred to in theory papers. The difference is not “G2 ignores practical science and G3 suddenly introduces it.” It is that G3 allocates 15% to a formal practical test, while G2 develops practical understanding as part of the learning and theory preparation.
For a student bridging upward, the key development is to move from describing a method to executing it accurately under examination conditions. That includes reading apparatus, recording units, controlling variables, presenting results and recognising limitations. Repeating a procedure without understanding why it is performed will not prepare the student for an unfamiliar practical task.
4. A simple example of the difference between the two levels
Imagine both a G2 and a G3 student are learning how to measure the density of a solid. Both need to understand mass, volume, the equation and units. Both should recognise that an irregular object needs an appropriate way to determine its volume. At G2, the learner may encounter a theory question that describes the method and supplies results. At G3, the candidate may need to carry out a practical task and produce valid measurements within the practical examination.
The scientific concept is related, but the assessment evidence differs. One paper may test whether the student can interpret the method and data; the practical paper tests whether the candidate can perform the relevant task and record evidence. That is why a G3 transition plan should include supervised practical experience, not simply harder written questions.
5. How to prepare for a G2-to-G3 Combined Science transition
- Confirm the intended G3 pairing: K326, K327 or K328. Do not assume the same two sciences will automatically be offered.
- Check topic coverage: compare the current G2 and G3 syllabuses rather than relying only on old subject names.
- Strengthen the first scientific prerequisite: units, variables, diagrams, calculations or scientific vocabulary as appropriate.
- Build structured-response stamina: explain the reasoning, not just the final answer.
- Practise interpreting experimental data: identify patterns, limitations and appropriate conclusions.
- Gain supervised practical familiarity: use school laboratory opportunities and teacher feedback.
- Test transfer: attempt unfamiliar contexts to establish whether the method works beyond a memorised question.
Students should not be pushed into an immediate level change solely because they score well on one topic. The school considers eligibility, overall readiness, curriculum continuity and availability. Parents should ask the subject teacher how a student’s performance across both sciences compares with the demands of the intended G3 combination.
6. Choosing the subject pair at each level
The same three scientific pairings exist at G2 and G3, but the level, content demands and examination structure differ. A family should consider interest and readiness in both disciplines, not just which science the student likes most. A candidate choosing Physics/Chemistry needs a plan for both; choosing Chemistry/Biology still requires genuine engagement with the two different forms of reasoning.
Future pathways should be checked separately. Certain post-secondary programmes specify science subjects or minimum grades, but there is no universal rule that one combined pair guarantees entry into every course. Review official course prerequisites for the actual admission year and discuss them with the school before deciding.
7. Past-year papers: why G2 and G3 booklets cannot be mixed casually
Older G2 N(A)-Level questions may help a learner practise concepts where they align with the 2027 SEC syllabus. G3 O-Level materials may also be useful for certain topics or skills. But a student must not assume the paper structure is the same. The G2 multiple-choice and structured pair for each science differs from G3’s shared MCQ, two structured papers and formal practical.
Make a resource list that records the K-code, discipline, paper type and topic. A question from G3 Pure Chemistry is not automatically a good replacement for a G2 Combined Science task, and a G2 Chemistry structured question does not replicate the demands of the G3 Practical test. Check the current syllabus first.
Frequently asked questions
What are the G2 Combined Science codes?
K223 Physics/Chemistry, K224 Physics/Biology and K225 Chemistry/Biology.
What are the G3 Combined Science codes?
K326 Physics/Chemistry, K327 Physics/Biology and K328 Chemistry/Biology.
Does G2 Combined Science have a separate practical exam?
The published K223/K224/K225 scheme lists the four discipline-specific theory papers and no separate national practical paper, although practical work is expected.
Does G3 Combined Science have a practical exam?
Yes. Paper 5 is a formal 1-hour-30-minute practical test worth 15%.
How many G3 structured papers does a candidate take?
Two of Papers 2, 3 and 4, according to the selected science pairing.
Is the G2 and G3 multiple-choice paper weighted the same?
G2 has one 20% MCQ paper for each science; G3 has one combined MCQ paper worth 20%.
Can a student move from K223 to K326 automatically?
No automatic transfer should be assumed. The school must consider eligibility, subject offering and readiness.
Related eduKateSG reading
For the G2 six-paper choice, read K223 vs K224 vs K225. For the G2 practical expectations, see the four-task laboratory guide. For G3 Pure Science, read the Pure Physics, Chemistry and Biology comparison.
Official sources
- SEAB — 2027 G2 Combined Science K223/K224/K225 scheme and practical guidance
- SEAB — 2027 G3 Combined Science K326/K327/K328 papers and Paper 5 practical assessment
- SEAB — G2 2027 syllabus index
- SEAB — G3 2027 syllabus index
Reviewed 7 November 2026 against SEAB’s published 2027 assessment schemes. Practical illustrations are original and are not experimental instructions. Follow school decisions and laboratory safety procedures.