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 this 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.
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State the reason why light is refracted as it crosses from air into glass. [1 mark]
Velocity/speed of the light decreases as it enters the glass .
Refraction is caused by light changing speed. If it gets faster, it bends away from the normal line. If it gets slower, it bends towards the normal line.
Describe one piece of evidence that shows when a sound wave travels through the air it is the wave and not the air itself that travels. [1 mark]
Any one of:
Some students investigate the properties of the waves generated in a ripple tank.
Student A says: 'The waves move water from one end of the tank to the other’.
Student B says: ‘That’s wrong. Only the waves move, not the water’.
Suggest what the students could do to decide which of them is correct. [2 marks]
Place a floating object/plastic duck on the surface of the water . It will stay in the same place and only bob up and down if the water doesn’t move .
Explain what happens to water waves as they pass into a deeper region. [2 marks]
They will speed up  so waves (wavefronts) move further apart .
Waves travel faster in deeper water and more slowly in shallow water. This is why tsunami waves are forced up to great heights as they approach the shallower water and land.