How IGCSE Combined Science (0653) is really marked
Combined Science 0653 is set across three tiers of practical routes (Papers 1/2 and 3, 4, 5/6) covering biology, chemistry and physics content in one syllabus. Papers 1, 2 and 3/4 (the theory papers) are almost entirely point-marked: 200 marks each on Papers 1 and 2, and 400 marks on the alternative-to-practical-style Papers 3 and 4, with the mark scheme listing specific acceptable answers for each response. Across the whole syllabus, 3,045 questions are points-marked against 207 marked by calculation — so the vast majority of marks come from stating the exact fact, term or observation the mark scheme wants, not from extended argument.
The calculation questions are concentrated but not trivial: Papers 3 and 4 carry 23 to 35 calculation questions each, and Papers 5/6 (practical) and 6/1–6/3 (alternative to practical) add a further handful. These follow the usual method-plus-answer convention, so correct working can still earn credit even if the final number is wrong — but only if the working is shown, not just the answer.
Papers 5 and 6 are practical-skills papers, and this is where technique separates candidates most sharply. Practical skills is the single largest topic area in the syllabus (96 questions), and it rewards precision in a specific way: correct apparatus named exactly, graphs drawn to the conventions asked for (labelled axes, sensible scales, the right kind of line), and conclusions that link back to the data given rather than repeating the question.
Where candidates actually lose marks
- Converting units incorrectly or not at all before a calculation — for example not converting a volume from cm3 to m3 by dividing by 10^6, so the wrong value is carried into the answer. (try the question)
- Dividing a mass by 10 to convert to a weight in newtons, rather than multiplying by the gravitational field strength. (try the question)
- On force diagrams, drawing the arrow so it does not touch the object it acts on — touching the vehicle or the air near the load instead of the load itself. (try the question)
- Explaining constant speed on a flat road by describing only the driving force, without mentioning the opposing frictional forces that balance it. (try the question)
- When asked to describe a decrease that is constant, writing only 'decreasing' or 'the deceleration was constant' without saying what was decreasing at a constant rate — this does not get credit. (try the question)
- Choosing imprecise points when measuring a wave's period from a graph, rather than two clear points such as where the trace crosses the time axis or two adjacent peaks. (try the question)
- Forgetting to square the speed term when substituting into a kinetic-energy-type calculation. (try the question)
- Confusing egestion with excretion, or naming the rectum instead of the anus, when describing the removal of solid waste from the gut. (try the question)
- Describing mechanical digestion as breaking down food molecules rather than breaking down pieces of food — a molecular description belongs to chemical digestion. (try the question)
- In graph-drawing questions, omitting axis labels or units, inverting the axes, or choosing a non-linear scale that does not use at least half the grid provided. (try the question)
Command words in IGCSE Science - Combined
| Command word | Times in our bank | What it demands |
|---|---|---|
| Identify | 1309 | Give the single correct name, structure or value the mark scheme is looking for — no explanation needed, but it has to be the precise term (e.g. 'anus' not 'waste outlet'). |
| State | 500 | Write a fact or value briefly and directly, with no supporting reasoning required or rewarded. |
| Calculate | 257 | Show your working as well as the final answer, with correct units — method marks are available even if the final figure is wrong. |
| Complete | 210 | Fill in a gap in a diagram, table or sentence with the missing term, value or label, matching the format already used around it. |
| Describe | 204 | Give an account of what is observed or what happens, in sequence if relevant, without needing to explain why. |
| Explain | 185 | Give a reason or mechanism — say why something happens, not just what happens, and include every linking step the mark scheme credits. |
| Suggest | 117 | Apply your science knowledge to a new or unfamiliar context; there may be more than one acceptable answer, but it must be scientifically sound. |
| Draw | 110 | Produce an accurate diagram, graph or ray path using a ruler where needed, following the conventions taught for that topic. |
How to revise with past papers
Because most marks in Combined Science 0653 are points-marked, past-paper practice pays off fastest when you check your answers against the exact wording the mark scheme accepts, not just whether you got the 'gist' right. Build a running list of the precise terms you keep losing marks on — egestion versus excretion, 'very acidic' versus 'acidic', formula versus word equation — and drill those specifically, since these are the kind of small wording slips that are easy to repeat.
For the calculation questions on Papers 3, 4, 5 and 6, practise showing full working every time, including unit conversions, even in questions you can do in your head. Papers 5 and 6 reward the habit of naming apparatus exactly and drawing graphs to the stated conventions (labelled axes, appropriate scale, correct line type) — these are learnable, mechanical skills that are worth rehearsing on real past papers rather than assuming you already have them.
This is a generic exam-technique point but worth repeating for a syllabus this points-dense: read the command word before you start writing. 'State' answers that turn into explanations waste time; 'Explain' answers that just state a fact lose marks. Timing yourself on past papers under exam conditions is the most reliable way to build this discipline before the real exam.
Practise real 0653 questions with AI marking →FAQs
Is Combined Science 0653 mostly about learning facts, or about calculations?
Mostly facts and precise terminology. Across the syllabus, 3,045 questions are points-marked against 207 marked by calculation, so recall and precise wording carry far more weight than maths.
Which papers include a practical element?
Papers 5 and 6 are the practical-skills routes, and practical skills is also the single biggest topic by question count (96 questions) — apparatus, graph-drawing and data-handling conventions matter here.
Do I need to show working for calculation questions?
Yes. Calculate questions carry method marks, so working shown (including unit conversions) can earn credit even when the final answer is wrong.
What's the difference between 'Describe' and 'Explain' in this subject?
Describe asks for what happens; Explain asks for why it happens. Answering an Explain question with only a description misses the reasoning marks.