Paper 1 Multiple Choice (Core): Complete 0620 Strategy
A complete Cambridge IGCSE Chemistry 0620 Paper 1 guide: 40 Core multiple-choice questions in 45 minutes, the grade C ceiling, distractor discipline, timing and review.
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 2026-08-24.
Paper 1 is the Core multiple-choice paper: 40 questions in 45 minutes, worth 30% of the qualification. It assesses Core content only. Paper 1 is one of the two written papers on the Core route (Paper 1 + Paper 3 + Paper 5 or 6), where the grades available are C to G. A grade above C requires the Extended route and its papers, which is explained in the Core vs Extended guide.
The format rewards three things at once: enough Core Chemistry to eliminate options, enough written working to avoid arithmetic traps, and enough review discipline to fix a repeated mistake instead of rehearsing it.
What Paper 1 tests
Even though it is Core, Paper 1 is not pure recall. Questions can require:
- precise recall of definitions, tests, colours, conditions and formulae
- interpretation of particle diagrams, apparatus, tables and graphs
- one-step calculations at Core level, such as relative formula mass or moles from mass
- comparison of close statements
- application of a Core principle to an unfamiliar example
- recognition of a practical method, variable, observation or conclusion
Paper 1 does not assess Supplement content. If a practice question depends on a Supplement-only rule, it belongs to Paper 2, not Paper 1. Confirming which route and paper you are entered for is worth doing early: see which paper am I taking.
The Core grade ceiling, stated plainly
Paper 1 cannot, on its own or combined with Paper 3, produce a grade above C. This is not a comment on effort or ability; it is how the route is structured. A Core candidate scoring near full marks still receives a C at most. If the destination requires a B, A or A*, the entry itself must be Extended before the examination series closes. Discuss any route change with the school’s exams officer well before the amendment deadline.
The four-pass timing method
This is a training structure, not an official Cambridge rule. Adjust it using timed evidence.
Pass 1: secure questions
Move through the paper without letting one hard item stall the whole attempt. Answer questions where the rule, fact or calculation route is clear. Mark questions that need more work.
Pass 2: calculations and diagrams
Return to items needing written working, careful particle counting, graph reading or equation ratios. Use the question paper for short calculations rather than holding every step mentally.
Pass 3: eliminate and decide
For remaining questions, cross out options that violate a definition, unit, trend, charge, atom count or practical principle. Select the best remaining answer even when certainty is incomplete.
Pass 4: targeted check
Check flagged questions and high-risk details:
- units and conversions
- positive and negative signs
- strongest versus weakest
- increase versus decrease
- atom versus molecule versus ion
- observation versus explanation
Change an answer only when you can identify the original error, not because of anxiety.
Distractor discipline
Every wrong option in a multiple-choice paper is designed to catch a specific error. The common families on a Core paper:
1. Unit distractors
A gas-volume or mass question may include answers produced by a factor-of-ten slip or a forgotten conversion such as 1000 cm³ = 1 dm³.
Defence: write the unit beside every quantity before selecting a formula.
2. Wrong-particle distractors
One mole of oxygen molecules contains one mole of O2 molecules but two moles of oxygen atoms.
Defence: circle the requested particle: atoms, molecules, ions or formula units.
3. Periodic-trend reversal
Options can reverse a trend down a group or across a period.
Defence: state the direction in words first. For example, Group I reactivity increases down the group.
4. Observation-conclusion confusion
“Bubbles form” is an observation. “Hydrogen is produced” is a conclusion supported by a test.
Defence: ask whether the option reports what was seen or what was inferred.
5. Similar-definition distractors
Options may swap atom, element, compound, mixture, oxidation or reduction wording.
Defence: learn definitions to mark-scheme precision, not by a vague example.
6. Practical-method distractors
Several pieces of apparatus may work, but only one measures the required quantity with suitable precision or without losing product.
Defence: identify the measurement first: mass, time, temperature, gas volume or fixed liquid volume.
A Core calculation routine
Use short written steps even for a one-mark question:
- Write the relationship. Example: moles = mass ÷ molar mass.
- Insert units or convert them. Example: 240 cm³ = 0.240 dm³.
- Calculate before reading the options closely. This reduces option-led guessing.
- Check scale and chemistry. A percentage cannot exceed 100% without a stated reason.
Original example: relative formula mass
What is the relative formula mass of Ca(OH)2? [Ar: Ca = 40, O = 16, H = 1]
A. 57
B. 58
C. 74
D. 75
Working: 40 + 2 × (16 + 1) = 40 + 34 = 74. Answer: C.
Option A ignores one hydroxide group; option B doubles only the oxygen.
The Paper 1 error log
For every incorrect question, record:
| Field | Example |
|---|---|
| Paper and question | 0620/11, Q12 |
| Topic | Stoichiometry |
| Error type | Formula mass |
| Wrong step | Counted one OH instead of two |
| Correct step | Multiply the whole bracket by 2 |
| Follow-up | Complete five fresh formula-mass questions |
Useful categories: missing fact, wrong formula, unit conversion, particle counting, trend direction, observation language, practical method, command or negative wording, rushed reading. The category determines the repair. Another full paper does not automatically fix a repeated unit error.
How Paper 1 differs from Paper 2
Paper 1 and Paper 2 share the format exactly: 40 questions, 45 minutes, 30% weighting, no negative marking. The differences are content and route:
- Paper 1 assesses Core content only; Paper 2 assesses Core plus Supplement.
- Paper 1 sits on the Core route (grades C to G); Paper 2 sits on the Extended route (grades A* to G).
- Paper 2 questions can demand deeper calculations and explanations that Paper 1 does not.
If you may switch routes, the Paper 2 multiple-choice guide shows the additional demands so you can judge the gap honestly.
Final check before the examination
A prepared Core candidate should be able to:
- finish within 45 minutes in practice
- leave no blanks
- show short working for calculations
- recognise recurring distractor types
- classify mistakes by cause and repair them
- keep accuracy steady across mixed Core topics
Use the free diagnostic to find your weakest Core topics, the topical questions and practice hub to repair them, and pair this guide with the Paper 3 theory (Core) guide so the same Chemistry works in structured answers. Browse all topic notes to close content gaps.