QWC 6 mark answer practice

In every AQA GCSE chemistry exam, candidates are expected to provide at least one long-style written answer. This is officially known as the question assessing Quality of Written Communication (QWC). Although, many candidates and teachers refer to this as the 6-mark question, as it is usually awarded 6 marks.

AQA have provided detailed guidance on how this question is structured and marked (click here)(link).

In these questions, candidates cannot obtain full marks unless they address BOTH the science content and the quality of English which includes spelling, punctuation and grammar, as well as writing in paragraphs, to ensure information appears clear and coherent. Neat writing is critical at this point.

In a 1 hour exam, worth 60 marks, a 6 mark question contributes to 10% of the exam mark and should take around 6-8 minutes to complete.

In QWC questions, the following criteria are used to assign marks:

Level 1: basic (1–2 marks)
Knowledge of basic information
Simple understanding
The answer is poorly organised, with almost no specialist terms and their use demonstrating a general lack of understanding of their meaning, little or no detail
The spelling, punctuation and grammar are very weak.

Level 2: clear (3–4 marks)
Knowledge of accurate information
Clear understanding
The answer has some structure and organisation, use of specialist terms has been attempted but not always accurately, some detail is given
There is reasonable accuracy in spelling, punctuation and grammar, although there may still be some errors.

Level 3: detailed (5–6 marks)
Knowledge of accurate information appropriately contextualised
Detailed understanding, supported by relevant evidence and examples
Answer is coherent and in an organised, logical sequence, containing a wide range of appropriate or relevant specialist terms used accurately
The answer shows almost faultless spelling, punctuation and grammar.

QWC Question: C1 Crude Oil

crude oil tower

In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

Describe and explain how petrol is separated from the mixture of hydrocarbons in crude oil.

Use the diagram and your knowledge to answer this question.

Model answer

Crude oil contains a mixture of hydrocarbons (grouped into fractions) with different boiling points. Fractional distillation is used to separate the fractions of hydrocarbons present in crude oil

Liquid crude oil is heated to around 350°C in a fractionating column and the crude oil vapour is passed into the column. The column has a deliberate temperature gradient: cool at the top and hot at the bottom. This means that vapour fractions with low boiling points condense where it is cooler (at the top of the column), whereas fractions with high boiling points condense where it is hotter (at the base of the column). The condensed fractions, now liquids, are collected through pipes positioned at different heights within the column.

Whilst this happens to most of the crude oil fractions, some crude oil fractions do not condense (e.g. natural gas, which has a very low boiling point and appears at the top of the column) or do not evaporate (e.g. liquid bitumen, which has a high boiling point and appears at the base of column). The petrol fraction will condense to liquid and be collected from the upper part of the column as it has a relatively low boiling point.

QWC Question: C1 Crude Oil


Evaluate replacing petrol with bioethanol as a fuel for cars. To gain full marks you should give a justified conclusion. Use the information from the table and your knowledge to answer this question.

Model answer

There are two main advantages of using bioethanol compared to petrol as a fuel. Firstly, ethanol can be made from a renewable source (e.g. sugar cane), whereas crude oil, being non-renewable, will eventually run out. Secondly, burning ethanol fuel is almost carbon-neutral as most of the CO2 released by ethanol combustion has arisen from atmospheric CO2 previously absorbed by the plant during photosynthesis.

There are several disadvantages of using bioethanol compared to petrol. Bioethanol is made by relatively slow batch processes involving several steps of fermentation and purification. In contrast, petrol is made using a relatively fast continuous fractional distillation process. Given that ethanol produces marginally less energy per litre than petrol, overall, there may be very little difference in costs between using ethanol or petrol as the main fuel. Furthermore, there is concern that converting large plantations to grow only crops useful for bioethanol production may threaten local ecology and species variation. Finally, there are clear ethical concerns in deciding whether food crops should be grown for bioethanol production given an ever increasing global food shortage.

QWC Question: C2 Electrolysis

filestore_aqa_org_uk_subjects_AQA-CH2HP-QP-JAN13_PDFThe electrolysis of sodium chloride solution produces chlorine and sodium hydroxide.

Use the information in the table and your knowledge to compare the environmental and economic advantages and disadvantages of using these two types of sodium chloride electrolysis cell.

Model answer

When deciding whether to use a mercury or membrane sodium chloride solution cell, it is important to consider their contrasting economic and environmental effects.

Overall the mercury cell delivers higher purity products (specifically Cl2 and NaOH), and the energy cost difference in its usage is only fractionally higher than the membrane cell.

However, the main disadvantage of the mercury cell is its initial high construction cost and its reliance on using a known toxic substance, mercury. Removing highly toxic mercury from the waste products of a mercury cell undoubtedly adds further costs and environmental hazards. This issue of toxic waste management does not arise with the membrane cell. Furthermore, the membrane cell has greater longevity as its membrane need only be replaced every 3 years, rather than repeatedly in the case of the mercury cell.

QWC Question: C2 Rate of reaction

filestore_aqa_org_uk_subjects_AQA-CH2HP-QP-JUN13_PDFIn this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. The student investigated how the rate of this reaction changed when the concentration of hydrochloric acid was changed.

Write a plan the student could use. In your plan you should:

  • describe how you would carry out the investigation and make it a fair test
  • describe the measurements you would make.

Examiner Mark scheme