IGCSE Chemistry 0620 Command Words: Decode Exam Questions for A*

IGCSE Chemistry command words are the action verbs in exam questions—such as state, define, describe, explain, calculate, suggest, and deduce—that tell you exactly what the examiner wants and how marks are awarded.

Mastering these instructions helps you match your response to the marking scheme, the relevant assessment objectives, and the expected level of chemical terminology.

The key is precise answering: Keep “state/define” concise, build clear cause–effect links for “explain,” show working and units for “calculate,” and justify ideas for “suggest/deduce.” When you train command words as a skill, you reduce avoidable errors, manage time better, and convert the same chemistry knowledge into a higher score.

Understanding IGCSE Chemistry Command Words To Boost Your Grade

In Cambridge IGCSE Chemistry, command words are not decoration; they are the marking instructions. Cambridge explicitly defines command words as terms that tell candidates how to answer a question and what the examiner expects.

Based on our years of practical tutoring at Times Edu, the fastest grade gains often come from training response discipline: Matching your depth, chemical terminology, and structure to the command word before you write a single sentence.

A critical detail most students overlook in the 2026 exam cycle is that Cambridge IGCSE Chemistry (0620) is assessed across three components, and command words appear heavily in Theory papers where AO1 and AO2 dominate the marking.

Why command words are “grade boundaries” in disguise

Grade thresholds move each session, but the underlying skill demand stays stable: Students who consistently hit command words convert the same knowledge into more marks. Cambridge ^[1] publishes grade threshold tables each series and explains how thresholds are set at component/option level.

This matters tactically because “I knew the chemistry” is not the same as “I wrote what the marking scheme rewards.” The marking scheme is built around assessment objectives (AO1, AO2, AO3), and command words are the examiner’s shorthand for which AO is being tested.

The high-yield strategy Times Edu uses with international-school students

From our direct experience with international school curricula, high achievers separate revision into two tracks:

• Content mastery (Chemical terminology): Definitions, equations, trends, key experiments.
• Response engineering (Action verbs): Command word recognition, mark-allocation planning, and marking-scheme phrasing.

You do not need “longer answers.” You need precise answering that maps to examiner expectations.

Command words you must be able to execute on demand

Cambridge lists a set of command words used in Chemistry assessments (0620) and defines what they mean (Analyse, Calculate, Compare, Deduce, Define, Describe, Determine, Discuss, Evaluate, Examine, Explain, Give, Identify, Justify, Predict, Show, Sketch, State, Suggest).

Below is a practical version of that list designed for exam execution, aligned to marking scheme behavior.

The official Cambridge definitions explicitly emphasise clarity, evidence, and proportion where relevant (for example, “sketch” requires key features and care over proportions).

Common misconceptions that quietly cap grades

1. “Explain” means “repeat the textbook.” It means: Write a causal chain that earns marks.
2. “Describe” should include reasons to sound smart. It often loses time and can drift off-marking-scheme.
3. “Suggest” is guessing. It is applied knowledge in an unfamiliar context, and Cambridge explicitly frames it as having a range of valid responses.
4. Overwriting is safer. Overwriting often creates contradictions, and examiners do not award marks for incorrect statements.

How this links to study-abroad subject strategy

Families often ask whether Chemistry is “worth it” for university admissions. For competitive STEM, medicine, engineering, and natural sciences, Chemistry is a credibility signal, but only if the grade is strong and supported by a coherent subject combination.

The pedagogical approach we recommend for high-achievers is to choose subjects that create a narrative: Chemistry + Maths (+ Biology or Physics) supports a clear academic spine, and command-word execution is a major driver of turning that narrative into an A/A* result rather than a mid-band grade.

>>> Read more: IGCSE Chemistry Mock Improvement Plan for 2026: Practical Steps to Improve After Every Mock Exam

The Crucial Difference Between “Describe” And “Explain” In Chemistry

“Describe” and “Explain” are the most frequently confused action verbs in IGCSE Chemistry. Cambridge’s own definitions make the contrast clear: “Describe” focuses on features/main points, while “explain” requires reasons and relationships supported by relevant evidence.

A two-line decision rule you can apply in the exam

• If the question is asking what you see / what happens / what changes, it is Describe.
• If the question is asking why / how / due to what chemistry, it is Explain.

What “Describe” looks like when it earns full marks

A high-scoring description has three traits:

• Uses observable or stated data (colour change, gas produced, temperature change, precipitate).
• Uses correct chemical terminology (effervescence, precipitate, aqueous, insoluble).
• Follows a logical sequence when relevant (before → during → after).

Example (Describe): “Bubbles are produced. The magnesium ribbon becomes smaller and disappears. A colourless solution remains.”

No extra chemistry is needed unless the question explicitly asks for it.

What “Explain” looks like when it earns full marks

An “Explain” answer is usually a chain of linked statements. A strong template is:

Cause (principle) → Mechanism (particle/ionic/electron story) → Result (what you observe).

Example (Explain): “Magnesium is above hydrogen in the reactivity series, so it loses electrons to form Mg²⁺. The H⁺ ions gain electrons to form hydrogen gas. This is why you observe effervescence.”

How to allocate marks inside “Explain” questions

Students often ask how many points to write for a 4-mark “explain”. Use the marking scheme mindset:

• 1 Mark is typically 1 correct, distinct chemistry point.
• A 4-mark “explain” often rewards a 4-step chain, not one long paragraph.

A practical structure is 4 bullet points, each a single causal step, each using precise terminology.

Examiner expectations for “Describe and explain” hybrids

A critical detail most students overlook in the 2026 exam cycle is that hybrid prompts are common in structured questions. If the prompt contains both verbs, the mark scheme usually separates them into two clusters of marks.

Your execution rule:

• Do “Describe” first (data/observations).
• Then do “Explain” (chemistry reasons).

>>> Read more: IGCSE Chemistry Past Paper Strategy for 2026: Smart Ways to Practice for Better Results

How To Interpret The Word State To Avoid Overwriting

“State” is one of the highest efficiency command words in the exam. Cambridge defines “State” as expressing something in clear terms, which is deliberately minimal.

Why students lose marks on “State” despite knowing the content

The problem is not knowledge; it is response control.

Common failure modes:

• Writing a paragraph and burying the answer.
• Adding an incorrect detail that cancels a correct statement.
• Giving an example when the question asked for a general statement.

The “one-line, one-mark” rule

If it is a 1-mark “State” question, produce:

• One line.
• One idea.
• No justification unless asked.
• Example: State the test for hydrogen.
  Answer: “A lighted splint produces a squeaky pop.”

When “State” needs a number, unit, or condition

Based on our years of practical tutoring at Times Edu, students underperform on “State” when a value is required.

Build a quick checklist:

• Does the question imply units (kPa, °C, g, mol dm⁻³)?
• Does it require conditions (catalyst, temperature, pressure)?
• Does it require a formula or symbol equation?

If yes, “State” must be precise, not verbose.

“State” vs “Define” vs “Give”

These words feel similar but behave differently in marking schemes. Cambridge distinguishes them: Define requires a precise meaning; give can be recalled from memory; state is a clear statement.

>>> Read more: IGCSE Chemistry Mistakes 2026: Common Errors Students Make and How to Avoid Them

Mastering Instructions Like Predict Suggest And Deduce

This cluster is where top grades are won, because it tests AO2: Handling information and problem-solving. Cambridge’s AO2 explicitly includes forming conclusions, making predictions, and solving unfamiliar problems.

Predict: Pattern → outcome

Cambridge defines “Predict” as suggesting what may happen based on available information.

Execution template:

• Quote the pattern (trend, relationship, data direction).
• State the outcome consistent with the pattern.

Common misconception: Predicting requires certainty.
It requires the most defensible outcome from the information provided.

Suggest: Applied chemistry with justification

Cambridge defines “Suggest” as applying knowledge to situations where there can be a range of valid responses.

A high-scoring “Suggest” answer has two components:

• A plausible idea that fits the context.
• A chemical reason that makes it defensible.

What not to do: List five guesses. Examiners reward quality, not volume.

Deduce: Inference, not memory dump

Cambridge defines “Deduce” as concluding from available information.

This is where students mistakenly introduce outside facts that are not needed. A clean deduce answer:

• Uses the data (mass change, gas volume, colour change, pH, conductivity).
• Uses one syllabus principle (reactivity, solubility rules, ionic charges, electrolysis rules).
• Concludes only what is supported.

A practical comparison table for these three

Where this links to grade thresholds and performance planning

Grade thresholds vary by series, but Cambridge publishes them openly for each session. For example, Cambridge provides official Chemistry (0620) grade threshold tables for June 2025 and November 2025.

From a coaching perspective, we use grade thresholds to set a margin strategy:

• Secure marks in command words that are “low-risk” (state, identify, calculate).
• Then train the “high-ceiling” verbs (explain, deduce, evaluate) to push into the next grade band.

That approach is stable even when thresholds move.

>>> Read more: IGCSE Chemistry Study Plan for 2026: A Simple Revision Guide for Better Exam Preparation

Guidelines For Drawing And Sketching Chemical Apparatus

Practical and diagram-based questions are not just “drawing ability.” They are assessed skills, and Cambridge explicitly lists drawing/completing/labelling apparatus diagrams as an expected experimental skill.

What “Sketch” specifically demands

Cambridge defines “Sketch” as a simple freehand drawing showing key features, with care over proportions.

This signals three marking scheme priorities:

• Key components included.
• Reasonable proportions (not artistic precision).
• Labels that identify, not decorate.

The Times Edu apparatus drawing checklist

Use this checklist whenever the command word is sketch, draw, label, or complete a diagram.

• Use single, clean lines.
• Avoid shading and 3D effects.
• Label with straight lines that touch the correct part.
• Keep labels horizontal and readable.
• Include essential features only (bung, delivery tube, condenser, thermometer position).

Common apparatus mistakes that lose marks

Based on our years of practical tutoring at Times Edu, these errors are repeat offenders:

• Thermometer bulb placed incorrectly (not in vapour path during distillation).
• Delivery tube drawn below liquid level when gas collection requires correct positioning.
• Missing direction of water flow in a condenser.
• Gas syringe drawn without a sealed system.

How to label like the marking scheme

Examiners typically award marks for correct identification of components and correct placement. Cambridge’s syllabus emphasises identifying apparatus and drawing/completing/labelling diagrams as part of AO3 skill expectations.

A practical rule:

• Label only what the question targets.
• If it is a 2-mark label task, label two items accurately rather than six vaguely.

Graphs and “sketching trends” in Chemistry

Students often forget that “sketch” can also apply to graphs. Cambridge’s guidance on graphing (axes labels, sensible scale, clear points, best-fit line) is part of the broader expectation for presenting data.

If you are asked to sketch a trend:

• Label axes with quantity and unit.
• Draw the correct curve shape and intercept behavior.
• Mark key points if given.

>>> Read more: IGCSE Tutor 2026: How to Choose the Right One

Frequently Asked Questions

Conclusion

If you want a predictable grade rise, stop revising Chemistry only as content. Train IGCSE chemistry command words as a skill system: Action verbs, marking scheme logic, assessment objectives, and examiner expectations.

Times Edu can map your current paper performance to a personalised 6–12 week plan (topic gaps, command-word weaknesses, and an exam-cycle strategy aligned to your target grade and intended university pathway). Reach out for a diagnostic consultation and we will tell you, with evidence, what to fix first and how to fix it fastest.

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