Six-mark questions
Six-mark questions are extended open response questions. These require longer answers than the structured questions that have fewer marks. It is wise to plan your answer first by making some notes. This will help you to include all the key points.
To gain full marks, you need to:
- support explanations using scientific knowledge and understanding
- use appropriate scientific words
- write clearly and link ideas in a logical way
- maintain a sustained line of reasoning
Writing six-mark answers with Dr Alex Lathbridge
Listen to the full series on BBC Sounds.
How to write six-mark answers in your science GCSE exams.
Six-mark questions often use these command words:
- Describe means you should recall facts, events or processes accurately. You might need to give an account of what something looked like, or what happened.
- Explain means you need to make something clear, or state the reasons for something happening.
- Compare means you need to describe similarities and differences between things. If you are asked to compare X and Y, write down something about X and something about Y, and give a comparison. Do not just write about X only or Y only.
- Evaluate means you must use information supplied, or your own knowledge, to consider the evidence for and against or to identify strengths and weaknesses. You must then complete your answer with a conclusion, stating which is better and why, for example.
Six-mark questions may be synoptic questions, which bring together ideas from two or more topics. For example, a question about fertilisers could include ideas about covalent substances, acids and alkalis, chemical calculations, and effects on the environment.
The answers shown here give marking points as bullet points. You do not usually need to include all of them to gain six marks, but you do need to write in sentences, linking them logically and clearly.
These questions have been written by Bitesize consultants as suggestions to the types of questions that may appear in an exam paper.
Sample question 1 - Foundation
Question
Methane is used as a fuel in most homes in the UK. It is burned in a boiler which is commonly located on an external wall in the kitchen. Air is drawn into the boiler from the outside through a tube called a flue, which is also used to get rid of the waste gases from the boiler.
Why is it essential that the flue is clear of any obstructions and what would be the consequences of a faulty or blocked flue? [6 marks]
The following are valid points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.
- A blocked flue would decrease the supply of air/oxygen to the boiler.
- This would lead to incomplete combustion.
- Incomplete combustion releases less energy.
- Incomplete combustion produces particulate carbon...
- ...which is dirty and can cause breathing difficulties.
- Incomplete combustion produces carbon monoxide...
- ...which is poisonous...
- ...because it binds to haemoglobin the blood and prevents it from carrying oxygen...
- ...but it is colourless and odourless, so not easy to detect...
- ...so the people living in the house would be in danger of poisoning/death.
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Sample question 2 - Foundation
Question
Ethanol can be produced via fermentation or by the direct reaction of ethene with steam. The table below summarises the two reactions.
| Fermentation | Direct hydration | |
| Chemical equation | glucose → ethanol + carbon dioxide | ethene + steam ⇌ ethanol |
| Raw materials | Sugar cane | Crude oil, water |
| Energy requirements | Can be done at room temperature | High temperature needed |
| Quantity of ethanol produced | Lower | Higher |
| Yield of ethanol | Maximum 13% | Effectively 100% because unreacted rectants are recycled |
| Atom economy | 39% | 100% |
| Chemical equation | |
| Fermentation | glucose → ethanol + carbon dioxide |
| Direct hydration | ethene + steam ⇌ ethanol |
| Raw materials | |
| Fermentation | Sugar cane |
| Direct hydration | Crude oil, water |
| Energy requirements | |
| Fermentation | Can be done at room temperature |
| Direct hydration | High temperature needed |
| Quantity of ethanol produced | |
| Fermentation | Lower |
| Direct hydration | Higher |
| Yield of ethanol | |
| Fermentation | Maximum 13% |
| Direct hydration | Effectively 100% because unreacted rectants are recycled |
| Atom economy | |
| Fermentation | 39% |
| Direct hydration | 100% |
Evaluate which of these methods is most effective for generating ethanol to be used in fuels for cars in a tropical country which does not have significant quantities of fossil fuel resources. [6 marks]
The following are valid points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.
- Hydration of ethene is a reversible reaction but fementation is not.
- Raw materials for fermentation are easier to obtain in a tropical country.
- ...because the climate will make growing sugar cane easy...
- ...and the country does not have large supplies of crude oil...
- ...so it would need to import/buy crude oil.
- Fermentation has a lower energy requirement...
- ...therefore it does not require the use of fossil fuels to generate electricity/heat for the reaction to occur.
- However, the quantity of ethanol produced is lower when using fermentation...
- ...and this might not match demand for the ethanol fuel.
- Fermentation produces a lower yield of ethanol...
- ...therefore further steps will be needed to concentrate the ethanol (distillation).
- Fermentation has a lower atom economy...
- ...which might suggest that the process is less sustainable than direct hydration...
- ...however, it uses a renewable raw material which can be grown on farmland.
- ...it is actually carbon neutral and therefore very sustainable.
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Sample question 3 - Higher
Question
A student is trying to distinguish between three colourless liquids. One of them is an alkene, one of them is an alcohol and the other is a carboxylic acid. Describe an experiment that would allow the student to identify which is which. You should state and explain the expected results in your answer. [6 marks]
The following are valid points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.
- Add a carbonate (solid or solution) to samples of the three liquids.
- The carboxylic acid will fizz...
- ...because carbon dioxide is made...
- ...which will turn limewater cloudy.
- Add bromine water to samples of the three liquids.
- The alkene will turn the bromine water from orange to colourless.
- Finally, the alcohol will show no reaction with both of these tests.
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Sample question 4 - Higher
Question
Poly(ethene) is a polymer which is made from ethene, C2H4, whereas polyesters are can be formed from a monomer which has two alcohol group and a monomer which has two carboxylic acid groups. Use equations to describe the difference between these two methods of producing polymers. [6 marks]
The following are valid points that could be included in your answer. It is important that you do not bullet point your answer but write your sentences in full.
- In addition polymerisation, many identical monomers are added together...
- ...with no other byproducts being made.
- ethene → poly(ethene)
- n C2H4 → (C2H4)n
- In condensation polymerisation, a small molecule is made as a by-product.
- When polyesters are made, the by-product is a molecule of water.
- nHO-▭-OH + nHOOC-▭-COOH → (▭-OOC-▭-COO)n + 2nH2O
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