One to two mark questions will start with command words such as 'describe' or 'explain'. Some command words are easy to understand such as:
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 a steep linear increase for the first three hours 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 '[2 marks]'. It is essential that you give two different answers if a question is worth two marks. Sometimes you can gain a second mark by giving the units in a calculation or stating specific data points, eg the speed of the object decreased by 8 m/s.
Edexcel questions courtesy of Pearson Education Ltd.
There are many different types of waves.
Waves on the surface of water are transverse waves. Sound waves are longitudinal waves.
Describe the difference between transverse waves and longitudinal waves. [2 marks]
Transverse waves have oscillations perpendicular to direction of travel of the wave . Longitudinal waves have oscillations in the same direction as the direction of travel of the wave .
This is a very common question and you should learn these definitions exactly.
Water waves are transverse waves.
a) Give one other example of a transverse wave. [1 mark]
b) Give one example of a longitudinal wave. [1 mark]
a) Light waves 
Only give one answer. If you put two answers, one of which is right and one of which is wrong, you will score zero. You could also have said seismic P-waves are longitudinal.
b) Sound wave 
Only give one answer. If you put two answers, one of which is right and one of which is wrong, you will score zero. You could also have said seismic S-waves are transverse.