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.
Kinetic theory describes the movement of particles in the three states of matter.
Gas is one of the states of matter.
Name the other two states of matter. [2 marks]
Solid  and liquid .
An espresso machine has a steam pipe that can be used to heat milk in a jug. Steam from the pipe enters the milk, where steam condenses to water. The steam and hot water heat the milk.
Describe, in terms of energy, how the arrangement and movement of particles in the steam changes as the steam enters the milk, condenses and cools. [2 marks]
When steam condenses, its molecules move closer together, so the internal energy decreases . When the water from the condensed steam cools, its molecules move more slowly, therefore storing less kinetic energy .