In SEC 2027 G2 Science Chemistry Paper 4, candidates taking K223 or K225 answer all of Section A and choose one of two eight-mark structured questions in Section B. Read the subparts in both choices before committing. A familiar heading can hide a calculation or explanation that you have not practised.
Choose by looking at what each subpart asks you to produce. A balanced equation, a data comparison and a chemical explanation need different kinds of working. The exercise below shows how to spot those demands quickly and make a decision.
- Read both choices down to the last subpart.
- Look for the evidence, calculations and explanations you can complete.
- Finish the selected question and check that you answered its command words.
Find the choice in the paper
The 30-mark Paper 4 is the structured Chemistry component for Science (Physics, Chemistry), K223, and Science (Chemistry, Biology), K225. Paper 3 is the Chemistry multiple-choice component. The syllabus allocates a shared 1 hour 15 minutes to Papers 3 and 4.
Section A contributes 22 marks. Its last question carries eight marks and is compulsory. Section B is the part that gives you the choice. When you practise, locate the section heading before deciding what to answer.
Worked choice | Rates of reaction or separation
Imagine Option A gives a table of gas volumes from two reactions. It asks you to compare the amount of gas collected in the first 20 seconds, explain why the smaller solid pieces react faster under otherwise identical conditions, and interpret why the curve levels off. Option B asks you to choose how to separate sand from salt solution, explain how to obtain salt from the filtrate and apply the same reasoning to a different mixture.
If you can read the rates table and explain surface area, scan the final subpart before choosing A. A curve that levels off shows gas collection has stopped increasing within the measurements. Use the conditions or evidence in the question if asked to identify which reactant was used up.
If you favour B, ask yourself whether you can name what passes through the filter and what stays behind. For a mixture of insoluble sand and dissolved salt, sand is the residue and salt solution is the filtrate. Use the remaining task wording to choose how to recover the salt. These are invented prompts for practising choice, with your teacher’s method taking priority for practical work.
Make a quick decision you can defend
For each choice, identify one subpart you can answer immediately and one that needs more thought. Check how many marks the harder subpart carries. A choice with one awkward first item and several manageable later ones can still suit you.
Distinguish an unfamiliar story from an unfamiliar idea. A question about gas production in a setting you have never heard of may still give the same kind of graph you know. Name the axes and units to see whether you can work with it.
Check dependencies. If one answer asks you to use a result from an earlier part, plan to show your working clearly. If two subparts stand independently, a difficulty with one need not prevent you from attempting the other.
Rehearse the choice, then check it
Use a pair of school-provided practice choices. Write a one-line reason for selecting one, answer it, then mark your work. Compare what you expected to be easy with what you could actually explain or calculate.
On a second practice, swap the order of the choices. Notice whether your decision changes because of the question order. A parent or study partner can ask you to name two things you would actually write before you choose.
Frequently asked questions
Can I skip the last question in Section A?
No. Section A is compulsory, including its final eight-mark question.
How many Section B questions should I answer?
Answer one of the two under the published scheme.
Is Paper 4 a laboratory practical?
For K223 and K225, Paper 4 is the structured Chemistry theory paper.
Official information
SEAB’s 2027 SEC G2 Science syllabus for K223, K224 and K225, Scheme of Assessment and Theory Papers. Checked 8 November 2026.