A-Level Chemistry Essay Questions: There are no essay questions. How to write "describe and explain" written response questions.

First, a quick note: A-Level Chemistry does not have an essay paper or essay questions. However, there are many written questions in Chemistry: explaining trends, explaining properties, describing reactions and observations, and describing mechanisms. The Cambridge 9701 syllabus frequently uses phrases like "describe and explain"; the Edexcel IAL syllabus specifies that papers for Units 2, 4, and 5 may include extended-writing questions. For calculation questions, see Chemistry Calculations; for data questions, see Chemistry Data Questions; and for practical questions, see Chemistry Practicals. This article focuses on written questions: the requirements and command words for both exam boards, and how to write common explanation questions. The references are the Cambridge 9701 syllabus (2025–2027) and the Pearson IAL Chemistry Specification (Issue 1).

1. Where to Find Written Questions

• Cambridge 9701: Paper 2 (AS) and Paper 4 (A Level) are structured questions, with written questions distributed across sub-questions. The assessment objectives for Papers 1, 2, and 4 are 50% AO1 Knowledge and understanding, and 50% AO2 Handling, application, and evaluation of information;
• Edexcel IAL: Section B of Units 2, 4, and 5 includes short-answer, open-response, calculation, and extended-writing questions; Section B of Unit 1 and the practical units, Units 3 and 6, only list short-answer, open-response, and calculation questions, without mentioning extended-writing questions.

The Cambridge syllabus also specifically reminds students: marks will be deducted for incorrect units and significant figures, which also applies to numerical values in written questions (see article 197).

2. Command Words

Cambridge syllabus definitions (excerpt): Describe—state points, give features and main characteristics; Explain—state purpose or reason, clarify relationships between things, explain why and/or how, and support with relevant evidence; Compare—identify or comment on similarities and/or differences; Contrast—identify or comment on differences; Deduce—draw a conclusion from given information; Predict—deduce what might happen from given information; Suggest—apply knowledge to propose a suggestion or opinion in a context with multiple valid answers; Discuss—present a detailed and organized argument; Evaluate—judge quality, importance, or value; Justify—support a viewpoint with evidence or reasoning.

The Edexcel command word table (common to all IAL sciences) is more specific. For example: Describe requires expanding on points but does not require giving reasons; Explain must include reasoning or justification; Compare and contrast must cover every item, including at least one similarity and one difference; Suggest involves applying knowledge in an unfamiliar context, which may include content not directly studied. The full table can be found in the article on Physics Written Questions, as both subjects use the same table.

3. "Explain" Requirements in the Syllabus

In the Cambridge 9701 A Level content, there are extensive requirements to "explain" or "describe and explain," and they often specify the angle from which to explain. Here are a few examples from the syllabus:

• Qualitatively explain the effect of ionic charge and ionic radius on lattice energy and enthalpy change of hydration;
• Describe and qualitatively explain the trends in the thermal stability of Group 2 nitrates and carbonates, including the effect of ionic radius on the polarization of large anions;
• Explain why transition elements exhibit variable oxidation states using the similar energies of the 3d and 4s subshells;
• Explain why transition element compounds are colored using the frequency of light absorbed when electrons transition between two non-degenerate d orbitals;
• Explain why arenes undergo substitution rather than addition reactions using electron delocalization (aromatic stability);
• Explain how buffer solutions control pH, and illustrate this using chemical equations.

These requirements themselves serve as an outline for answering: if the syllabus says "in terms of," your answer must use that specific angle (empirical advice).

4. How to Write Common Written Questions

Here is some empirical advice:

1. Explaining Trends

First, describe the trend (increasing/decreasing down a group or across a period), then explain the reason in terms of structure: atomic or ionic radius, nuclear charge, electron shielding, type and strength of bonding, and intermolecular forces. Write out every step, for example, "increased ionic radius → decreased charge density → decreased polarization of anions → more stable carbonate."

2. Explaining Properties (Acidity, Basicity, Reactivity)

When comparing two substances, identify the structural differences, then explain how this difference affects the property. For example, when comparing the basicity of amines and amides, mention the availability of the lone pair on the nitrogen atom.

3. Describing Reactions and Observations

Clearly state the reagents, conditions, observations, and products; observations should be specific, such as the color change from what to what, or whether a precipitate or gas is formed. If applicable, write a balanced equation.

4. Describing Mechanisms

Use curly arrows to show the movement of electron pairs, labeling partial charges, lone pairs, and intermediates; the arrow starts from the electron pair and points to the atom or bond accepting the electrons (follow the conventions in your textbook and mark scheme).

5. Comparing and Evaluating

For comparison questions, address both sides for every point; for evaluation questions (Suggest, Evaluate), combine the information given in the prompt to state the strengths and weaknesses, and provide a well-reasoned judgment.

5. Common Reasons for Losing Marks

Here is an empirical summary:

• In Explain questions, only describing the observation without explaining the reason in terms of structure;
• Skipping steps in the causal chain, such as directly writing "larger radius so more stable";
• Confusing concepts, such as "atom," "ion," and "molecule," or "bond" and "intermolecular force";
• Writing vague observations, such as just writing "color change";
• Drawing the direction or starting point of arrows incorrectly in mechanisms.

Conclusion

Chemistry does not have essay questions, but "describe and explain" runs throughout the entire syllabus. The Cambridge syllabus specifies the angle for many explanation questions, while Edexcel includes extended-writing questions in Units 2, 4, and 5, with a command word table that clearly distinguishes between describing and explaining. By writing a complete causal chain from the angle specified in the syllabus, using accurate terminology, specific observations, and balanced equations, you can consistently score well on written questions. If you need A-Level Chemistry tutoring, feel free to chat with our teachers.

Verification note: This article was verified in September 2026. The assessment objective weightings for each Cambridge 9701 paper, the specific notes on units and significant figures, the command word definitions, and the learning requirements cited in Part 3 are from the Cambridge International Chemistry 9701 syllabus for 2025, 2026 and 2027. The question type descriptions for each Edexcel IAL Chemistry unit (Units 2, 4, and 5 include extended-writing questions, which are not listed for Units 1, 3, and 6), as well as the command word table (Appendix 7 of the syllabus, common to IAL Physics and other sciences), are from the Pearson IAL Chemistry Specification (Issue 1). The writing advice and common reasons for losing marks are our empirical suggestions.

References:

• Cambridge International: Chemistry 9701 Syllabus 2025–2027 (PDF)
• Pearson Edexcel: International A Level Chemistry Specification (PDF)