G2 Combined Science in the 2027 SEC is offered in three subject pairings: K223 Physics/Chemistry, K224 Physics/Biology and K225 Chemistry/Biology. SEAB publishes six possible paper components, but a candidate takes only the four papers belonging to the two sciences in the chosen pairing. Each science contributes half of the overall subject result: one 20-mark multiple-choice paper worth 20% and one 30-mark structured paper worth 30%. The result is therefore built from 50% Physics, 50% Chemistry for K223; 50% Physics, 50% Biology for K224; or 50% Chemistry, 50% Biology for K225.
This matters when choosing Secondary 3 subjects and buying revision books. “G2 Combined Science” is not one universal paper set. A student offering K224 does not sit the Chemistry pair of Papers 3 and 4; a K225 student does not sit Physics Papers 1 and 2. The correct code determines the two disciplines, the four paper numbers, and the topic coverage. Parents should read the entry record and the exact 2027 syllabus before planning a revision timetable.
SEC 2027 G2 Combined Science: pairings at a glance
| SEC code | Subject pairing | Four papers taken | Overall contribution |
|---|---|---|---|
| K223 | Science (Physics, Chemistry) | 1 Physics MCQ; 2 Physics Structured; 3 Chemistry MCQ; 4 Chemistry Structured | Physics 50% + Chemistry 50% |
| K224 | Science (Physics, Biology) | 1 Physics MCQ; 2 Physics Structured; 5 Biology MCQ; 6 Biology Structured | Physics 50% + Biology 50% |
| K225 | Science (Chemistry, Biology) | 3 Chemistry MCQ; 4 Chemistry Structured; 5 Biology MCQ; 6 Biology Structured | Chemistry 50% + Biology 50% |
For each science, the multiple-choice paper is 20 marks and 20%; its structured paper is 30 marks and 30%. Each pairing therefore totals 100 marks and 100%. SEAB states that the relevant pair of papers is taken in one session lasting 1 hour 15 minutes. Candidates are advised not to spend more than 30 minutes on each multiple-choice paper in that session.
Official source: the joint SEAB K223/K224/K225 G2 Science 2027 syllabus and the 2027 G2 school-candidate subject list.
1. Why does SEAB list six papers if the student takes only four?
SEAB uses a common paper numbering system across the three possible pairings. Papers 1 and 2 belong to Physics, Papers 3 and 4 to Chemistry, and Papers 5 and 6 to Biology. A candidate’s registered K-code selects two of these three discipline pairs. This keeps each science’s assessment components recognisable while allowing the student to study two sciences rather than all three.
The subject code is the safeguard against confusion. A student with K223 takes Physics and Chemistry. A student with K224 takes Physics and Biology. A student with K225 takes Chemistry and Biology. Do not assume that a school can substitute an individual paper from another pair simply because a learner has studied that topic in class.
Within each discipline, Paper 1, 3 or 5 is multiple choice with 20 compulsory questions. Paper 2, 4 or 6 is structured. The structured paper contains Section A worth 22 marks, with compulsory questions, and Section B worth 8 marks, with two structured questions from which the candidate answers one. The exact content still follows the selected pairing’s syllabus and topic coverage.
2. How should a family choose Physics/Chemistry, Physics/Biology or Chemistry/Biology?
The strongest decision is not simply “Which pair is easiest?” It is a comparison between the student’s interests, existing foundations, school offering, workload and possible later-course requirements. A learner may enjoy understanding physical systems and chemical changes; another may be more interested in forces and living organisms; a third may prefer chemical processes and biological systems.
K223 Physics/Chemistry joins two sciences in which quantitative relationships, models and particle-level explanations are important. Students need confidence with measurement, units, formula use and the links between observations and explanations. It can suit learners who enjoy both physical systems and how substances behave, but it is not a Mathematics-only subject: scientific interpretation and practical reasoning matter too.
K224 Physics/Biology combines measurement and physical models with living systems. It asks students to move between numerical or graphical representations and biological structures or processes. A learner may need to adapt their thinking from equations and units in one topic to cause-and-effect explanations across cells, organisms or ecosystems in another.
K225 Chemistry/Biology combines chemical reactions and material properties with living systems. The connection can be intellectually interesting because biological processes depend on chemical interactions, but the student must still understand the different language and evidence used in each discipline. A strong Biology student should not assume Chemistry will be easy simply because both subjects concern matter and life.
Check admissions before treating a subject pair as a pathway
Some post-secondary courses require particular subjects or grades; others have different entry combinations. Do not promise that one G2 pairing automatically qualifies a student for a specific course. Check the actual polytechnic, ITE, JC or other programme requirements for the intended admission year, including whether a later G3 subject or bridging arrangement is relevant. School subject availability and eligibility must be checked separately from national syllabus availability.
3. The two disciplines each contribute half: what does that mean for revision?
Each component is equally weighted within its science: MCQ 20% plus structured 30% equals 50%. This means a student cannot safely neglect the structured paper and expect excellent performance from multiple choice alone. Equally, a learner who writes long structured explanations but repeatedly misreads simple MCQ conditions is leaving marks behind.
A practical plan separates the two disciplines and the two question forms. For example, a weekly schedule might alternate a Physics concept and structured question with a Chemistry concept and structured question, then include shorter retrieval sessions for both MCQ components. The exact balance should respond to the student’s performance, not an arbitrary assumption that each topic takes the same amount of time.
Keep an error log with four categories: concept misunderstanding, reading the question incorrectly, calculation or unit error, and incomplete explanation. If the student writes “the temperature went up” when the question asks why it increased, the problem may be explanation rather than memory. If the student selects the wrong MCQ because they miss a word such as “not”, the correction is close reading, not another full chapter.
4. How to use an unfamiliar question to test whether the concept transfers
After a learner has understood one worked example, change a condition. Change the numbers, diagram, biological context or chemical setting. Ask them to explain why the same principle still applies—or why it no longer does. A student who can repeat a memorised solution but cannot adapt it may have recognised the surface pattern without understanding the underlying relationship.
For example, a Physics calculation can be altered by changing a unit or asking for a different unknown. A Chemistry question can provide a new observation and ask what conclusion is justified. A Biology question can change one environmental factor and ask how the process may respond. The student should be able to state what changed in the question and why that changes the reasoning.
5. How to avoid buying the wrong Combined Science past-year papers
Check these details on the resource before using it:
- The year and qualification match the student’s preparation purpose.
- The subject code or old reference code matches the discipline pairing.
- The paper number belongs to the selected science.
- The topic is actually included in the current K223, K224 or K225 syllabus.
- The assessment format still aligns with the 2027 SEC paper structure.
Older N(A)-Level material can still provide useful practice where its topic and question type align. It should not be treated as a complete substitute for the new SEC syllabus. A publisher’s cover saying “Combined Science” is not enough: K223, K224 and K225 are different candidate entries.
6. Does G2 Combined Science have a practical examination?
The published K223/K224/K225 assessment scheme lists four theory papers for the chosen pair: one multiple-choice and one structured paper for each science. It does not list a separate national practical paper in the way the G3 Pure Science syllabuses specify Paper 3 Practical. However, practical work remains a required part of learning and the syllabus expects students to be familiar with laboratory techniques and investigations.
That distinction is important. “No separate practical paper in this scheme” does not mean practical skills are irrelevant, nor does it mean students should learn experiments only by reading descriptions. Practical methods and observations can be referenced in theory questions. The centre is responsible for safety, and the actual learning activities should be completed under appropriate school supervision.
7. A two-week decision and diagnostic plan
| Period | Action | Evidence to collect |
|---|---|---|
| Days 1–2 | Confirm K223, K224 or K225 and map the four papers | Correct pairing, topics and paper numbers |
| Days 3–4 | Try a short MCQ set from each selected science | Concept errors versus question-reading errors |
| Days 5–6 | Attempt one structured question from each science | Ability to explain, calculate and show reasoning |
| Days 7–8 | Revisit one weak prerequisite in each science | Can the learner explain the basic relationship unaided? |
| Days 9–10 | Use changed examples or diagrams | Can the method transfer beyond a memorised question? |
| Days 11–12 | Review laboratory observations and practical feedback from school | Can the learner distinguish observation from inference? |
| Days 13–14 | Reattempt the weakest tasks after a gap | Independent correction rather than copied answers |
Frequently asked questions
What is the difference between K223, K224 and K225?
K223 is Physics/Chemistry, K224 is Physics/Biology and K225 is Chemistry/Biology. Each candidate takes the four papers belonging to the two sciences selected.
Does a G2 Combined Science candidate sit six papers?
No. SEAB lists six possible papers across the three science disciplines; each candidate takes four papers for their registered pairing.
How much is each science worth?
Each of the two selected sciences contributes 50%: 20% multiple choice and 30% structured response.
How long are the paper pairs?
The relevant pair of multiple-choice and structured papers for one science is taken in a 1 hour 15 minute session.
Is there a separate national practical paper for G2 Combined Science?
The published K223/K224/K225 scheme lists four papers and no separate national practical paper. Practical learning is still expected and practical techniques may be tested through theory questions.
Can a student switch from K223 to K224 just before the examination?
Subject entry changes are not a casual paper choice. Ask the school about current eligibility, timetable and registration deadlines.
Related eduKateSG guides
For the comparison with G3 Pure Science, read SEC Pure Physics, Chemistry and Biology. For the practical expectations that support G2 learning, see Science practical preparation across G1/G2/G3. For subject combinations, see the Secondary 3 choice guide.
Official sources
- SEAB — 2027 G2 Combined Science K223/K224/K225 syllabus, six-paper structure and practical guidance
- SEAB — 2027 G2 subject catalogue
- SEAB — SEC qualification and examination overview
Reviewed 7 November 2026 against the official 2027 G2 Science syllabus. Examples are original teaching illustrations. School subject availability, eligibility and final candidate entries should be confirmed with the school.