Structured and short answers
Questions with one to four marks usually start with command words. If a question starts with the command word 'state', 'give', 'name' or 'write down', it needs a short answer only. This type of question can often be answered with one word or phrase.
It is important to state, give, name or write down the number of things that the question asks for. If you write down fewer, you cannot get all the marks. If you write down more, and one is wrong, you might lose a mark.
Learn about command words with Dr Alex Lathbridge
Listen to the full series on BBC Sounds.
Understanding the different command words in your science GCSE exams.
Some questions start with the command words 'describe', 'explain' or 'compare'. These are often worth two or more marks:
- Describe means you should recall facts, events or processes accurately. You might need to give an account of what something looked like, or what happened.
- Explain means you need to make something clear, or state the reasons for something happening. The points in the answer must be linked together. The answer must not be a list of reasons. All the points must be relevant to the question.
- Compare means you need to describe similarities and differences between things. If you are asked to compare X and Y, write down something about X and something about Y, and give a comparison. Do not just write about X only or Y only.
More complex structured questions will be worth three or four marks. They include questions with complex descriptions and explanations, and questions in which you need to compare things.
Some of the answers are shown here as bullet points. This is to show clearly how a mark can be obtained. However, do not use bullet points in your answers - the points must be linked together logically.
This page contains AQA material which is reproduced by permission of AQA.
Sample question 1 - Foundation
Question
The rate of the reaction between dilute acid and calcium carbonate can be investigated by doing the reaction on a top pan balance and measuring the change in mass every ten seconds. Use the symbol equation below to explain why there is a loss in mass during this reaction.
2HCl(aq) + CaCO3(s) → CaCl2(aq) + H2O(l) + CO2(g) [2 marks]
A gas is produced [1]
Which escapes from the flask [1]
Sample question 2 - Foundation
Question
Describe an alternative way of measuring the rate of the above reaction, which does not involve measuring the mass change of the reaction. [2 marks]
Collect the gas in a gas syringe or inverted measuring cylinder in a water bath [1]
Measure the volume of gas produced every ten seconds [1]
Sample question 3 - Higher
Question
Explain, in terms of particles, why the rate decreases during the reaction between magnesium and hydrochloric acid. [2 marks]
The concentration of acid decreases over time [1]
So collisions are less frequent [1]
Sample question 4 - Higher
Question
The equation below shows one stage in the manufacture of sulfuric acid from sulfur dioxide.
2SO2(g) + O2(g) ⇌ 2SO3(g)
The reaction is exothermic in the forward direction.
Use le Chatelier's principle to predict the effect of increasing the temperature on the amount of sulfur trioxide (SO3) produced at equilibrium. Give a reason for your answer. [2 marks]
Decreases [1]
Because the position of equilibrium moves to the left, in the endothermic direction, to counteract the increase in temperature. [1]
