From Drilling to Explaining: Why A-level Chemistry Rewards Reasoning

Many students arrive at A-level Chemistry with excellent study habits built on practice: working through large numbers of similar questions until the method is automatic. Fluency with calculations and equations matters, and drilling builds it.

But A-level Chemistry also asks students to do something drilling alone cannot fully prepare them for: to reason through problems they have not seen before, and to explain that reasoning in writing. This guide explains why, using the official AQA A-level Chemistry (7405) specification and examiners' reports, and suggests how students can keep the benefits of practice while building the reasoning skills the exams reward.

What the exams are designed to test

AQA's specification sets out three assessment objectives (AOs) for A-level Chemistry:

• AO1: demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures;
• AO2: apply knowledge and understanding, in theoretical and practical contexts;
• AO3: analyse, interpret and evaluate scientific information, ideas and evidence, to make judgements, reach conclusions and refine practical procedures.

The specification gives approximate weightings across the whole A-level: about 30% for AO1, 45% for AO2 and 25% for AO3 (AQA specification, section 4.3). In other words, roughly 70% of the marks are for applying, analysing and evaluating, rather than recalling.

What examiners say

AQA's published examiners' reports show recurring themes that point to the same gap between knowing and reasoning.

Unfamiliar contexts separate students. Commenting on a 2022 Paper 2 question, the examiners wrote: "This question required students to deduce and add three curly arrows to an unfamiliar incomplete mechanism. As with similar questions in the past, this discriminated well between the most able and weaker students."

Correct answers without enough reasoning can still lose marks. On a 2022 extended-response question, examiners noted: "Students often failed to reach the highest level because their answers lacked sufficient detail, despite arriving at the correct overall structure." The final answer was right; the explanation of how they got there was not complete enough.

Stating is not the same as explaining. In a 2019 question on chromatography, examiners reported "many students simply stating that the amino acids had different solubilities or different Rf values in different solvents without explaining that some had the same Rf value in solvent 1 hence the need to use solvent 2." The students knew the relevant fact. What they did not do was link it to the specific situation in the question.

Reading the question is part of reasoning. On a 2022 Paper 3 practical question, examiners noted: "Some students ignored the instruction in the question about the same apparatus being used and suggested a different thermometer or the addition of insulation." A memorised answer was applied to a question that had ruled it out.

Showing the reasoning matters. On a 2023 mechanism question, examiners observed: "Some students struggled because they did not show the mechanistic steps using curly arrows." The reasoning needed to be visible on the page.

These are selected examples, not a statistical summary, but the marks students miss are often for reasoning and linking, not for missing knowledge.

Why drilling is not enough on its own

Repeated practice of identical question types trains students to apply a fixed method. That is less helpful when:

• a question is set in a context the student has not seen, such as an unfamiliar molecule or industrial process;
• two topics are combined in one question;
• the question asks why a method works, not just what the answer is;
• marks are awarded for each step of a logical argument.

Students who have learned mainly by drilling sometimes describe A-level questions as "unfair" or "not in the syllabus". Usually the Chemistry is in the specification; the context is new. That is by design.

A short example

Imagine a question asking why adding acid shifts an equilibrium. A drilled answer might say: "The equilibrium shifts to the right." That states a result. A reasoned answer names the equilibrium, says which species the added H+ ions react with, and links that change in concentration to the direction of shift. Examiners have commented on this exact gap, noting that some students "referred to the shifting of an equilibrium without identifying it".

Moving from drilling to explaining

Practice is still essential. The change is in how students practise. Some approaches that help:

• Ask "why?" after every answer. After completing a calculation or a mechanism, explain in one or two sentences why each step is done. If you cannot, that is the gap to work on.
• Vary the context. Instead of ten questions on the same molecule, try the same principle on different molecules, or questions from different papers and years.
• Practise extended answers. Write full answers to longer questions under timed conditions, then compare them with the mark scheme. Check whether every link in the argument is there.
• Read the examiners' reports. They are free on the AQA website and describe what strong and weak answers looked like for each question.

Advice for parents

You do not need to be a chemist to help. Notice how your child is studying, not just how long. Hours spent repeating the same type of question may feel productive, but mixing in explanation and unfamiliar problems is usually a better use of the time. Ask them to explain a recent topic to you in plain terms.

This shift is a common one for students who come from systems that place more emphasis on practice and recall. It is a change of habit, not a sign that a student is less able.

Related reading

• Why Students Who Excelled at GCSE Chemistry Can Struggle at A-level — and How Parents Can Help
• Why Re-reading Chemistry Notes Is Not Enough: A 4-Week A-level Revision Plan

Where to go next

Help your child combine regular Chemistry practice with explaining each step and applying ideas to unfamiliar questions.

Free AQA A-level Chemistry Guide (in English): a clear overview of the AQA A-level course. Get the free guide

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