How A-Level Chemistry Is Marked: Mark Scheme Guide

A-Level Chemistry is marked point by point against a mark scheme, and the same few habits decide most of the marks: showing working, writing precise chemical language, and drawing mechanisms exactly. Extended answers are marked differently, by level of response, and that is where many students lose marks they thought they had earned.

This guide covers how A-Level Chemistry papers are marked at AQA and Edexcel, what the wording in a mark scheme means, and the mistakes that cost the most marks. Your specification and teacher are the final word on your own paper.

The exam boards and their papers

There are three main routes, and the chemistry is largely the same across them. What differs is how it is split across papers.

• AQA A-Level Chemistry (7405). Three written papers. Paper 1 is mainly inorganic and physical chemistry, Paper 2 mainly organic and physical, and Paper 3 can draw on any content and tests practical skills. The practical endorsement is reported separately from the A-Level grade, as a pass or not classified.
• Edexcel A-Level Chemistry (9CH0). Also three written papers: one on advanced inorganic and physical chemistry, one on advanced organic and physical chemistry, and a third on general and practical principles. Practical skills are assessed through the written papers and through the practical endorsement, which is again reported separately.
• Edexcel International A Level (IAL) Chemistry. Unit-based rather than three big papers. The AS units and the A2 units are examined separately, and there are practical-skills units too. Check your own specification for the exact units and sitting options.

Mark totals and timings have changed between specification versions, so confirm them against your board’s current specification rather than a past paper from a few years ago. You can browse each course by topic on Exaim: AQA A-Level Chemistry, Edexcel A-Level Chemistry and Edexcel IAL Chemistry.

How an A-Level chemistry mark scheme works

Every mark scheme is a list of marking points. Each point is a separate mark, and you earn it by writing something that matches it. A scheme usually shows the expected answer, then guidance in two short words that matter more than they look: allow and ignore.

• Allow lists alternative answers that still earn the mark. It is how the scheme tells examiners which different wordings are acceptable.
• Ignore lists things that neither earn nor lose the mark. If you add a harmless extra, it is ignored. But if you add something that contradicts the correct point, the mark can be lost.
• Contradictions. A correct statement followed by a wrong one in the same answer often scores nothing. Write the answer once, cleanly, instead of listing every term you can think of.
• Specific terms. Some marks need an exact phrase. “Lone pair repels more than bonding pair” earns what “the shape changes” does not. See what a mark scheme actually is for the general idea.

A-Level chemistry mark scheme: calculations, ECF and significant figures

Calculations carry method marks, exactly as at GCSE (see how method marks work), but the stages are longer: moles, then ratio from the equation, then mass, concentration, volume or an equilibrium constant. Each stage can earn its own mark.

The key idea is error carried forward (ECF). If you make a slip early on and then use that wrong value correctly, later marks can still be awarded. This only works when the examiner can see what you did, so write each step on its own line and label it.

• Units. A missing or wrong unit can cost the final mark, especially for rate constants, K_c and enthalpy changes, where the unit is part of the answer. Work out the unit from the expression, do not guess it.
• Significant figures. Schemes often accept a range, but an answer given to far too many or too few figures can lose the final mark. Match the data in the question, and do not round in the middle of a calculation.
• The sign. In energetics, a correct magnitude with the wrong sign usually scores less. Decide whether the reaction is exothermic or endothermic, then check your sign agrees.

Extended answers: level of response

Long answers, often six marks on AQA and Edexcel, are not marked point by point. They are marked by level of response. The examiner reads the whole answer, decides which level it fits (for example, a few relevant points with gaps in the reasoning, or a complete, logically ordered argument) and then places it within that level.

Two things lift an answer into the top level: the chemistry has to be correct and relevant, and it has to be linked. A list of correct facts with no reasoning between them stays in a lower level. The same applies at GCSE, so the advice in six-mark questions carries over: plan briefly, answer the question that was asked, and join each point to the next with “because” or “so”.

Mechanisms and curly arrows

Organic mechanisms are one of the most reliably marked parts of the paper, and one of the easiest places to lose marks without realising.

• Where the arrow starts. A curly arrow shows the movement of a pair of electrons. It must start from a lone pair, a negative charge or a bond, not from an atom or a nucleus.
• Where it ends. It must point to the atom or bond that receives the electrons. An arrow that stops short or points at nothing in particular can lose the mark.
• Charges and partial charges. Include the δ+ on the carbon being attacked and the full charge on any intermediate, such as a carbocation. Leaving them out can cost a mark even when the arrows are right.
• Half arrows. Radical mechanisms use single-headed arrows for single electrons. Using a full arrow, or the other way round, is a common slip.
• Name the mechanism. If the question asks for the type, such as nucleophilic substitution or electrophilic addition, a correct drawing may not score without the correct name.

Practical skills

Practical work appears in two ways. The endorsement is assessed by your teacher during the course and is reported separately. Practical skills are also tested in the written papers, in questions on method, apparatus, uncertainty, titration calculations and evaluating a procedure. Here, vagueness loses marks: name the apparatus, say what you measure and to what precision, and give a reason for each step.

The mistakes that cost the most marks

• Hidden working. A wrong final answer with no working scores zero. A wrong answer with clear working can still earn most of the marks.
• Loose language. Saying “atoms” when you mean “ions”, or “stronger” when you mean “more concentrated”, loses the mark in explanations.
• Wrong or missing units. Especially in kinetics and equilibria, where the unit is derived, not remembered.
• Mechanism arrows that start in the wrong place. The most common marked-down detail in organic chemistry.
• Answering a different question. Writing about what happens when the question asks why it happens. Read the command word first, as with command words at GCSE.
• Contradicting yourself. Adding an extra statement that cancels a correct one.

How to practise

These habits only show up when someone marks your answer against the real scheme and points to the exact mark you dropped. That feedback loop is the point of practising with past-paper style questions rather than rereading notes. On Exaim every written answer is marked against the board’s mark scheme, point by point, so you can see that your method earned the marks but the unit did not.

Start with the free notes, flashcards, mind maps and worksheets for A-Level Chemistry, organised by topic and subtopic for each board.