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 the 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.
Edexcel questions courtesy of Pearson Education Ltd.
A battery charger is connected to the 230 V ac domestic mains supply.
The output voltage of the charger is 335 V and it provides a dc charging current.
Charging stops if the charging current exceeds 15 A.
Explain how electrical components in the charger can be connected together to give this type of output. [6 marks]
First the pd must be converted from 230 V to 335 V. This can be done using a step-up transformer . The transformer's primary coil is connected between the live and neutral in the primary circuit . A diode is then needed to convert the ac into dc.  This should be connected in series with the secondary coil of the transformer and the battery to be charged . The charging current can be limited to 15 A using a fuse or a circuit breaker . A circuit breaker would be better than a fuse, since a fuse would need to be replaced after use .
Plan the key points which you should include in your answer. Break the question down into the stages necessary and then carefully describe each of these: increase from 230 V to 335 V, conversion from ac to dc, and switching off at currents above 15 A.
A traffic sign uses many small lights, all powered by a rechargeable battery.
These lights need to be very bright during the day so that they can be seen clearly.
They do not need to be as bright at night.
Explain how using a light-dependent resistor can make the energy stored in the battery last longer. [6 marks]
Because the sign doesn’t need to be as bright at night, less current is needed . At night the resistance of the LDR would increase  as it is darker . Higher resistance will allow less current to flow . Less current in the circuit means less energy per second is needed from the battery . So the total energy transferred is less during night time than it is during the day .
Plan the key points which you should include in your answer. Consider the current flowing in the circuit and the effect a change in the resistance of the LDR would have on it. If the current decreases then less energy is transferred from the battery, so the battery lasts longer.