Cambridge IGCSE Physics (0625) is the most widely sat science examination in the GCC and Southern Africa. It is also the examination where the gap between understanding physics and scoring physics is widest. A Candidate can understand every concept on the syllabus and still lose 15–20 marks through mark-scheme errors that have nothing to do with physics knowledge.
What follows are five specific errors identified through examiner marking experience — the errors that appear in Cambridge IGCSE Physics scripts consistently across series, that cost Candidates marks consistently, and that are consistently preventable with the right preparation.
Error 1: Describing instead of explaining
The most frequent instruction in Cambridge IGCSE Physics mark schemes is "explain" — not "describe", not "state", not "list". The distinction is precise. A description says what happens. An explanation says why it happens, using the correct physical mechanism.
A Candidate asked to explain why a metal rod expands when heated who writes "the rod gets longer when heated" has described the observation. The mark scheme requires the mechanism: "the metal ions vibrate with greater amplitude when heated, taking up more space, causing the rod to expand." The description earns zero marks. The explanation earns full marks.
Error 2: Correct physics, wrong units
Cambridge IGCSE Physics mark schemes award marks for the correct numerical answer including the correct unit. A correct number with the wrong unit — or no unit — does not earn the accuracy mark (A1) in calculation questions. This is applied consistently and without exception.
The units that cause the most errors are: pressure (Pa vs N/m², both acceptable but kPa is not unless the question uses kPa), speed (m/s vs km/h — always use m/s unless specified), and energy (J vs kJ — always use the unit that matches the data given).
Error 3: The "and" trap in two-mark questions
Two-mark questions in Cambridge IGCSE Physics frequently require two distinct points. The mark scheme awards one mark per point. A Candidate who writes two sentences that say the same thing — even if both sentences are correct — earns one mark, not two.
The pattern appears most frequently in questions about electromagnetic induction ("state two ways to increase the induced EMF"), thermal energy transfer ("explain two ways in which heat is lost from a house"), and forces ("give two differences between weight and mass"). In each case, the mark scheme defines two specific, distinct points. Rewording the same point twice does not earn the second mark.
Error 4: Drawing graphs without the three required features
Cambridge IGCSE Physics regularly requires Candidates to draw or complete graphs. The mark scheme for graph questions awards marks for three independent features: correct axes with units, correctly plotted points, and an appropriate line or curve of best fit. Each feature is marked separately. Each can be lost separately.
The most common loss is the line of best fit — Candidates who connect points dot-to-dot rather than drawing the best straight line through the data. Cambridge examiners are instructed to look for a single ruled line that minimises the distance to all plotted points. A dot-to-dot does not earn this mark, regardless of how accurately the individual points are plotted.
Error 5: Using colloquial language in definitions
Cambridge IGCSE Physics mark schemes for definition questions require precise scientific language. A Candidate who defines pressure as "how much force is pushing on something" has given a colloquial description. The mark scheme requires: "force per unit area" or "force divided by the area over which it acts." The colloquial answer earns zero marks.
Definitions that consistently cause mark-scheme failures: density ("how heavy something is for its size" vs "mass per unit volume"), power ("how fast energy is used" vs "rate of energy transfer or work done per unit time"), and moment ("the turning effect of a force" — this one is actually acceptable in the mark scheme, but Candidates who write "the force times the distance" without specifying perpendicular distance lose the mark).
Why these five errors are preventable
None of these errors require greater physics knowledge. They require mark-scheme knowledge — the specific language, structure, and conditions that Cambridge IGCSE Physics examiners are instructed to reward. This knowledge does not come from reading the textbook. It comes from working with someone who has marked the papers.
Learn the mark scheme from the examiner who applied it.
EMI IGCSE Physics Masterclasses are led by current and former Cambridge CAIE examiners. Every Masterclass is structured around mark-scheme deconstruction — the specific language and structure the examiner rewards. Cohorts of 15 Candidates. All Masterclasses recorded. Free first Masterclass, no card required.
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