Understanding IGCSE Chemistry Mark Schemes
How to read and use 0620 mark schemes to improve your exam answers -- what the marks mean, how examiners apply them, and how to use schemes as a revision tool.
Published by IGCSEChemistry.com.my
Chemistry teaching team: K. S. Tan (15+ years teaching IGCSE Chemistry) and Ms Yash (10+ years teaching IGCSE Chemistry) and Ms Kartini (15+ years teaching IGCSE Chemistry).
Mapped to Cambridge IGCSE Chemistry 0620 (2026–2028). Last updated 2026-08-19.
The mark scheme is the most underused resource in IGCSE Chemistry revision. Every student has access to it. Very few read it properly. Fewer still use it as a revision tool. Students who study the mark scheme alongside past papers understand what the examiner wants and stop losing marks on answers that are “close but not quite right.”
How mark schemes work
Marks and mark points
Each question on a 0620 paper is worth a specific number of marks. The mark scheme lists the mark points — the specific pieces of information or steps that earn each mark. A 3-mark question has three mark points. You must hit all three to score full marks.
Example: “State three differences between ionic and covalent bonding” (3 marks)
- Mark point 1: Ionic bonding involves transfer of electrons; covalent bonding involves sharing of electrons.
- Mark point 2: Ionic bonding occurs between a metal and a non-metal; covalent bonding occurs between non-metals.
- Mark point 3: Ionic compounds form a lattice; covalent compounds may form simple molecules or giant structures.
Each mark point is independent. If you get the first wrong but the second and third right, you score 2 marks, not 0.
Required words and acceptable alternatives
Mark schemes show the “ideal” answer and, in brackets or after a semicolon, acceptable alternatives. The ideal answer is the safest one to learn. Acceptable alternatives are usually less precise but still score.
Example:
- Required: “electrostatic forces of attraction between oppositely charged ions”
- Acceptable: “strong forces between positive and negative ions” (less precise but still scores)
- Not acceptable: “the ions are stuck together” (too vague, no mention of electrostatic attraction or charges)
When studying mark schemes, learn the required answer. If you use the ideal phrasing, you always score. If you use an alternative that is not listed, you may not.
OWTTE and ecf
OWTTE stands for “or words to that effect.” This appears when the examiner accepts any reasonable phrasing of the same idea. But “reasonable” has limits — the scientific content must be correct even if the wording varies.
ecf stands for “error carried forward.” If you make an error in part (a) and use that incorrect answer correctly in part (b), the examiner can still award marks in part (b) for correct method applied to the wrong value. This is why showing working in calculations is essential: even if the answer is wrong, the method marks are recoverable.
Reject marks (R)
Some mark schemes explicitly list answers that are rejected. These are common misconceptions or vague statements that do not score despite sounding plausible. For example, in a bonding question, “the bonds are strong” might be explicitly rejected because it does not specify which bonds.
Studying rejections is extremely valuable. They tell you exactly what the examiner does not want, which is often what most students write.
Using mark schemes as a revision tool
Step 1: Do the past paper first
Always attempt the paper before looking at the mark scheme. Marking an unattempted paper teaches you what the answers are, not whether you can produce them. The learning comes from comparing your answer with the scheme.
Step 2: Mark word-for-word
Do not approximate. Compare your answer to the mark scheme line by line:
- Did you use the correct scientific term?
- Did you include all mark points?
- Did you write anything that would be rejected?
- Did you show sufficient working for calculation marks?
If you are unsure whether your answer matches, err on the side of marking it wrong. This is revision, not a grade — being strict with yourself now prevents losing marks in the real exam.
Step 3: Note the language
Pay attention to the precise language the scheme uses. If it says “electrostatic forces” and you wrote “attraction,” you may have lost the mark. Copy the exact phrasing the scheme uses into your glossary or onto a flashcard. This is how you build the precise vocabulary the exam rewards.
Step 4: Read the examiner report
When available, the examiner report accompanies the mark scheme and explains common errors, how many students scored each mark, and what the examiner was looking for. This is direct insight into the marking process. If the examiner report says “most candidates wrote ‘the particles move faster’ but did not mention activation energy,” you know that mentioning activation energy is what separates a good answer from a weak one.
Common mark scheme patterns
”One mark for the equation, one mark for balancing”
Equation questions typically award one mark for correct formulae and one mark for correct balancing (including state symbols if required). This means an unbalanced equation with correct formulae still scores 1/2. Always attempt the equation even if you cannot balance it.
”One mark for the observation, one mark for the conclusion”
Qualitative analysis questions separate what you see from what it means. “A white precipitate forms” is the observation. “Zinc ions are present” is the conclusion. Students who jump straight to the conclusion and skip the observation lose one mark. See the qualitative analysis guide.
”Explanation in terms of particles/electrons/bonds”
When the scheme specifies “in terms of,” your answer must use that framework. “Explain in terms of particles why temperature increases the rate” requires you to talk about particles, collisions, and kinetic energy. An answer about activation energy that does not mention particles may score partial marks but not full marks.
”Reject: reference to atoms when should be ions”
Bonding and electrolysis questions distinguish between atoms, molecules, and ions. Writing “sodium atoms” when the answer is “sodium ions” is rejected. This distinction costs marks repeatedly. Train yourself to check: is the particle charged? If yes, it is an ion, not an atom.
The mark scheme as feedback loop
The most effective use of mark schemes is cyclical:
- Do a past paper under timed conditions.
- Mark against the scheme. Log every lost mark with the reason.
- Study the content you got wrong.
- Re-sit the failed questions one week later.
- Mark again. If you now score full marks, the gap is closed. If not, the study was insufficient — go deeper.
This cycle converts past paper practice from a testing exercise into a learning exercise. The mark scheme is the teacher that tells you exactly what was wrong and exactly what the right answer looks like. Use it as one.
Most students treat the mark scheme as a scoring tool. The students who improve fastest treat it as a learning tool. Every mark scheme you read teaches you what the examiner values, what language scores, and what common mistakes to avoid. Over eight weeks of structured practice, this learning accumulates into a significant exam technique advantage.