Paper 2 Multiple Choice: Complete 0620 Strategy
A complete Cambridge IGCSE Chemistry 0620 Paper 2 guide: 40 questions in 45 minutes, distractor analysis, calculation checks, timing, review and an error-log method.
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 2026-08-11.
Paper 2 is the Extended multiple-choice paper: 40 questions in 45 minutes, worth 30% of the qualification. The challenge is not simply speed. Each option is designed to look plausible to a student making a specific Chemistry error.
A useful Paper 2 method therefore has three parts:
- know enough Chemistry to eliminate options
- show enough working to avoid mental-arithmetic traps
- review the reason for every wrong choice
What Paper 2 tests
Questions can require:
- precise recall of definitions, tests, colours, conditions and formulae
- interpretation of particle diagrams, apparatus, tables and graphs
- one-step or multi-step calculations
- comparison of close statements
- application of a syllabus principle to an unfamiliar example
- recognition of a practical method, variable, observation or conclusion
The paper covers Core and Supplement because it is for Extended candidates.
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 allowing one hard item to stall the whole attempt. Answer questions where the rule, fact or calculation route is clear. Mark questions needing 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
- Core fact versus Supplement rule
- observation versus explanation
Do not use the final minute to reconsider every answer without a reason. Change an answer only when you can identify the original error.
The main distractor families
1. Unit distractors
A gas-volume question may include answers produced by using 24 with cm³ instead of 24,000, or by forgetting that 1000 cm³ = 1 dm³.
Defence: write the unit beside every quantity before selecting a formula.
2. Inverted-ratio distractors
Equation questions often offer the result from reversing the mole ratio.
Defence: write the balanced equation and place the known and unknown substances underneath it.
3. 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.
4. Periodic-trend reversal
Options can reverse a trend down a group or across a period.
Defence: state the direction in words before choosing an option. For example, Group I reactivity increases down the group.
5. 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.
6. Similar-definition distractors
The options may swap atom, element, compound, mixture, isotope, oxidation or reduction wording.
Defence: learn definitions in mark-scheme precision rather than by a vague example.
7. Practical-method distractors
Several pieces of apparatus may work, but only one may measure the required quantity with suitable precision or without losing product.
Defence: identify the measurement first: mass, time, temperature, gas volume or fixed liquid volume.
8. Condition distractors
Organic and industrial questions often mix correct reagents with conditions belonging to another reaction.
Defence: revise reaction-reagent-condition-product as one unit.
A calculation routine that survives pressure
Use four written steps:
- 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% unless the question context explains why an apparent value is invalid.
Original example 1: gas volume
A gas occupies 480 cm³ at r.t.p. How many moles are present?
A. 0.0020
B. 0.020
C. 0.20
D. 20
Working: 480 ÷ 24,000 = 0.020 mol.
Answer: B.
Option A can result from an extra factor-of-ten error. Option C can result from using 2400 rather than 24,000.
Original example 2: particles
How many oxygen atoms are present in 0.50 mol of O2 molecules?
A. 0.50 × 6.02 × 10²³
B. 1.00 × 6.02 × 10²³
C. 1.50 × 6.02 × 10²³
D. 2.00 × 6.02 × 10²³
Each molecule contains two oxygen atoms. 0.50 mol of O2 therefore contains 1.00 mol of oxygen atoms.
Answer: B.
Reading particle diagrams
Before counting:
- identify what each symbol represents
- decide whether touching symbols form a molecule or formula unit
- distinguish elements from compounds
- count complete particles, not individual circles, when the question asks for molecules
- check whether more than one substance is present
A mixture can contain only elements, only compounds or both. “Mixture” describes the presence of more than one substance, not a particular type of particle.
Handling graph and table questions
Use the sequence:
- read both axes or headings and their units
- identify the variable changed
- read values with the correct scale
- describe the pattern before explaining it
- use data from the question rather than a memorised trend if they differ
For rate graphs, the gradient represents rate. The final height can represent total product. A steeper curve does not automatically mean more product overall.
How to eliminate options with Chemistry
Do not rely on “which one looks right”. Test each option against a rule.
For an ionic formula:
- calculate the charge total
- reject any formula that is not electrically neutral
For an equation:
- count each atom on both sides
- reject an equation that is not balanced
For a qualitative test:
- check reagent
- check observation
- check whether a confirmatory test is needed
For bonding:
- identify particle type and structure
- connect the property to the force or mobile charged particle actually present
The Paper 2 error log
For every incorrect question, record:
| Field | Example |
|---|---|
| Paper and question | 0620/22, Q17 |
| Topic | Stoichiometry |
| Error type | Unit conversion |
| Wrong rule used | Divided cm³ by 24 |
| Correct rule | Divide cm³ by 24,000 at r.t.p. |
| Follow-up | Complete five fresh gas-volume questions |
Useful error categories:
- missing fact or definition
- wrong formula or equation
- unit conversion
- mole ratio
- particle counting
- trend direction
- observation language
- practical method
- command or negative wording
- rushed reading
- calculator entry
The category matters because it determines the repair. Another full paper does not automatically fix a repeated unit conversion error.
A weekly Paper 2 cycle
Session 1: topical accuracy
Choose one weak topic and complete a small set without timing pressure. Explain every option, including why the distractors are wrong.
Session 2: mixed timed set
Complete 15-20 mixed questions under time pressure. Record confidence beside each answer.
Session 3: repair
Review wrong and low-confidence answers. Return to the exact concept, then complete fresh questions testing the same rule.
Session 4: full-paper checkpoint
Use a full Paper 2 periodically to test timing and whether repaired errors stay repaired in a mixed context.
Common mistakes
- Doing every calculation mentally. One written line prevents many ratio and power-of-ten errors.
- Leaving questions blank. There is no negative marking.
- Changing answers based on anxiety. Change only when a specific error is identified.
- Reviewing only the correct option. Explain why each distractor is wrong.
- Recording only a total score. A score does not reveal the repair needed.
- Repeating full papers without topical correction. This rehearses the same mistake.
- Ignoring low-confidence correct answers. A lucky correct response still indicates unstable knowledge.
- Assuming Paper 2 is pure recall. It also tests calculations, data and application.
Final check before the examination
A prepared student should be able to:
- finish within 45 minutes in practice
- leave no blanks
- show short working for calculations
- identify recurring distractor types
- classify mistakes by cause
- explain why the rejected options are wrong
- maintain accuracy across mixed topics
Use the topical questions and practice hub to repair individual weaknesses, then pair this guide with the Paper 4 theory guide so the same Chemistry can be expressed in structured answers.