Six-mark questions
Six-mark questions are extended open-response questions. These require longer answers than the structured questions with fewer marks. It is wise to plan your answer rather than rushing straight into it, otherwise you may stray away from the key points.
Six-mark questions are marked using a levels-based mark scheme because they are open-ended. To gain full marks, you need to:
- support explanations using scientific knowledge and understanding
- use appropriate scientific words and terms
- write clearly, linking ideas in a logical way
- maintain a sustained line of reasoning, rather than getting lost or bogged down
You are likely to see command words such as:
- 'describe' - you need to give an account but no reason
- 'explain' - you must give reasons or explanations
- 'devise' - you must plan or invent a procedure using your scientific knowledge and understanding
- 'evaluate' - you must review information, including identifying strengths and weaknesses, and make a supported conclusion
Six-mark questions may be synoptic questions. This means they 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.
Remember that the topics covered in the first paper are assumed knowledge for the second paper, so questions in the second paper may need knowledge and understanding of those topics too.
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 full sentences, linking them logically and clearly.
Sample question 1 - Foundation
Question
Carbon monoxide and oxides of nitrogen are made in car engines.
Explain how these compounds are made in car engines, and describe the problems caused by carbon monoxide.
[6 marks]
OCR Gateway Science, GCE Chemistry, Paper B741, January 2013.
The following are vaild 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.
Carbon monoxide:
- carbon monoxide is made by incomplete combustion of fuel/petrol/diesel when there is not enough oxygen supplied to the fuel
- poisonous/toxic
- can kill people
- binds to haemoglobin in red blood cells
- reduces the amount of oxygen in the blood
Oxides of nitrogen:
- nitrogen and oxygen in air
- react together at high temperatures inside engines
Sample question 2 - Foundation
Question
Carbon dioxide and methane are greenhouse gases. They help to keep the Earth warm.
Describe the greenhouse effect, and the potential effects of increased levels of these gases. Include examples of how human activities are leading to emissions of carbon dioxide and methane.
[6 marks]
This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.
The following are vaild 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.
Sources of carbon dioxide:
- burning hydrocarbon fuels/fuels containing carbon
- manufacturing processes, eg cement manufacture, steel production
Sources of methane:
- cattle farming/rice farming
- natural gas exploration/leaky gas pipelines
Greenhouse effect:
Energy transferred from the Sun to the Earth's surface by radiation
- warm surface emits infrared radiation
- greenhouse gases absorb energy in infrared radiation
- this warms up the lower atmosphere
Potential effects:
- glaciers melting/polar ice melting
- sea levels rising
- rainfall changing/floods/droughts
- habitats changing
Sample question 3 - Higher
Question
Mars and Earth are both rocky planets. Their early atmospheres were produced by volcanic activity. They were similar, and were mainly carbon dioxide and water vapour.
The table shows the composition of the atmosphere of Mars today. This is very different from the composition of the Earth’s atmosphere today.
| Gas | Proportion today (%) |
| Nitrogen | 1.9 |
| Oxygen | 0.15 |
| Carbon dioxide | 96 |
| Water vapour | Trace amounts |
| Other gases | 1.9 |
| Gas | Nitrogen |
|---|---|
| Proportion today (%) | 1.9 |
| Gas | Oxygen |
|---|---|
| Proportion today (%) | 0.15 |
| Gas | Carbon dioxide |
|---|---|
| Proportion today (%) | 96 |
| Gas | Water vapour |
|---|---|
| Proportion today (%) | Trace amounts |
| Gas | Other gases |
|---|---|
| Proportion today (%) | 1.9 |
Describe, using information from the table, how the atmosphere of Mars has changed over time. Compare these changes to how the Earth’s atmosphere has changed. Explain how the changes to the Earth’s atmosphere occurred.
[6 marks]
OCR 21st Century Science, GCE Chemistry, Paper A171, May 2015.
The following are vaild 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.
Mars changes:
- percentage of carbon dioxide has increased
- percentage of water vapour has decreased
Earth changes:
- percentage of carbon dioxide has decreased
- percentage of water vapour has decreased
- percentage of oxygen has increased
- percentage of nitrogen has increased
Reasons:
- Earth cooled and water vapour condensed
- oceans formed
- carbon dioxide dissolved in the oceans
- photosynthesis
- plants released oxygen
- plants removed carbon dioxide