Six mark questions are often the questions that people find the most difficult. In all longer answer questions, but especially the six mark ones, it is important that you plan your answer and not just rush into it. After all, you would plan an essay or short story before starting. Without a plan it is easy to stray away from the key point and lose marks, get steps in a process in the wrong order or forget key bits of information.
Six mark questions will start with command words such as 'describe' or 'explain'. The command words 'describe' and 'explain' can be confusing. If you are asked to describe a graph, you will be expected to write about its overall shape, whether it is linear or curved, the slope of gradients etc. If you are asked to explain why a pattern or trend is seen in a graph, you will be expected to use your science knowledge not just say what you see (which is a description), eg 'The graph shows the number of radioactive nuclei decreases as time increases. It does this because…'.
'Explain how' and 'why' questions often have the word 'because' in their answer. 'Describe' questions don't.
The number of marks per question part is given in this form '[6 marks]'. It is essential that you give as many different points in your answer as possible, linking these together. Often, you will be asked to compare two things - make sure that you include both in your answer otherwise, you are likely to limit your score to two marks out of six marks.
This page contains AQA material which is reproduced by permission of AQA.
A man is driving his car at a constant speed on a wet road.
He sees a fallen tree on the wet road and tries to stop quickly to prevent an accident.
Explain why the man may not be able to stop in time. [6 marks]
The overall stopping distance depends on the thinking distance  and the braking distance . The thinking distance may be longer if the driver is distracted, tired or has been drinking alcohol . The braking distance may be longer as the wet road will mean there is less friction between the road and the tyres than there is in dry conditions . Braking distance will also be longer if the driver has less tread on their tyres  or if the tyres are not inflated to the correct pressure .
A strong answer will be clearly worded with good use of scientific key words. It may include the following points:
Two girls, A and B, ran an 800 m race.
The graph below shows how the distance changed with time:
Compare the motion of runners A and B.
Include data from the figure above.
Runner A starts at a faster speed than runner B  and maintains this constant speed for the first 440 m . After this, she begins to slow down and her speed decreases through the rest of the race . Runner B starts at a slower speed  but accelerates to reach a higher top speed than runner A . Runner B overtakes runner A at 700 m and wins the race by 34 s .
You will need to describe the race and also include the meaning of the changing gradients of both lines. You could include the following ideas:
A swimmer's speed increases as she begins to swim.
The swimmer has a top speed.
Explain why. [6 marks]
As she swims there is a drag force from the water . As her speed increases, so does the drag force  meaning the resultant force is less, and she accelerates less . When the drag force is equal to the thrust force, the resultant force will be zero and she will no longer accelerate and will travel at a constant speed . This top speed is her terminal velocity .
A strong answer will be clearly worded with good use of scientific key words. In this question, the key idea is linking the idea of balanced forces to her top (constant) speed.