The Exam Papers » Command Words in Physics Exams
What you'll learn this session
Study time: 30 minutes
Edexcel spec: Command word taxonomy (Appendix 5)
- Know what each command word in the Physics exams asks you to do
- Tell describe, explain and evaluate apart, and plot and sketch apart
- Set out a show that answer
- Avoid the common ways marks are lost
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Unlock This CourseWhy command words matter
Every exam question starts with a command word. It tells you what kind of answer the examiner wants. You can know all the physics and still lose marks by giving the wrong kind of answer, for example a description when the question said explain.
The specification lists the command words and what each one means. This lesson puts them into five groups. Read the question, spot the command word, then match your answer to it.
Key terms:
- Command word: the word at the start of a question that tells you what to do, such as describe, calculate or evaluate.
Group 1: recall and selecting
| Command word | What it asks for |
|---|---|
| Give / State / Name | These are really synonyms. They generally need you to recall one or more pieces of information. |
| Identify | Usually you select some key information from what you are given. |
| Add / Label | Add or label something on the material in the question, for example labelling a diagram or adding units to a table. |
| Complete | Complete a table or diagram. |
| Give a reason | A statement has already been made, and you only need to give the reason why. |
| State what is meant by | The meaning of a term is expected, but there are different ways to describe it. |
These answers are usually short. Do not add extra explanation, because it earns nothing and uses time.
Group 2: describe, explain and evaluate
These three are the ones students mix up most. Take one situation: a metal spoon is left in a hot drink.
📝 Describe
Give an account of what happens. The statements need to be developed and are often linked, but you do not need to give a reason.
🔍 Explain
Give a justification of a point. The answer must contain some reasoning. This can include mathematical explanations.
⚖️ Evaluate
Review the information, bring it together and reach a supported judgement, using strengths, weaknesses and the context.
Worked example: the same spoon
Describe what happens to the spoon. [2 marks]
The end in the drink gets hot first (1). The handle slowly gets warmer as well (1). No reason is needed.
Explain why the handle gets warm. [2 marks]
The particles in the hot end vibrate more (1). They pass energy along the metal to their neighbours, so the handle warms up (1). Now there is a reason.
Evaluate whether a metal spoon or a plastic spoon is better for a very hot drink. [3 marks]
A metal spoon is strong, but its handle gets hot. A plastic spoon keeps a cool handle, but is less strong and may bend when stirring thick food. Overall a plastic spoon is better for a hot drink, because a hot handle is the main problem in this context. A weighing-up of both sides, then a conclusion, is what makes it evaluate.
Group 3: calculations
- Calculate: obtain a numerical answer, showing relevant working.
- Determine: the answer must have a quantitative element from the stimulus, or show how the answer can be reached quantitatively. To get full marks there must be a quantitative element.
- Estimate: find an approximate value from a diagram or given data, or through a calculation.
- Show that: verify the statement given in the question.
For show that the answer is already given, so the marks are for the working. Write the equation, substitute the numbers, work it out, then state that it matches.
Worked example
A cyclist speeds up from 2 m/s to 17 m/s in 10 s. Show that the acceleration is 1.5 m/s2. [3 marks]
Equation: acceleration = (final velocity − initial velocity) ÷ time taken (1)
Substitution: a = (17 − 2) ÷ 10 (1)
Answer: a = 15 ÷ 10 = 1.5 m/s2, which matches the value in the question (1)
Group 4: graphs and diagrams
| Plot | Sketch | |
|---|---|---|
| What you do | Mark points accurately on a grid from the data given, then draw a line of best fit through them | Produce a freehand drawing |
| Scale | Needs a suitable scale and labelled axes, if they are not provided | The axes are not scaled |
| Must show | Accurate points and a line of best fit | A line and labelled axes, with important features indicated |
Draw means produce a diagram, using a ruler or freehand.
Group 5: judgements and thinking
- Comment on: bring together a number of variables from the data or information to form a judgement.
- Deduce: draw or reach conclusions from the information provided.
- Discuss: identify the issue being assessed, then explore all aspects of it by reasoning or argument.
- Justify: give evidence to support a statement in the question or an earlier answer.
- Predict: give an expected result.
- Suggest: use your knowledge to propose a solution to a problem in a new context.
- Design: plan or invent a procedure from existing principles or ideas.
Some questions put a verb in front of a command word. Analyse the data / graph to explain means examine the data or graph in detail to give an explanation. Your reasoning should point to numbers or features you can see.
In multiple-choice questions the direct command words are What, Why and Which.
Common ways marks are lost
Common mistakes
- Describing when the question says explain. If there is no reason, there is no reasoning mark.
- Explaining when the question says describe. It wastes time.
- Ignoring the marks in brackets. A 1-mark question needs one point, and a 4-mark question needs about four.
- Giving a calculation answer with no working or no unit.
- Evaluating with only one side, or with no conclusion.
- Plotting points carelessly, or drawing a sketch with no labelled axes.
- Using the word it when it is not clear what it is.
Exam-style question
A car speeds up from 5 m/s to 15 m/s in 4 s.
(a) State the name of the quantity that is the rate of change of velocity. [1 mark]
(b) Show that the acceleration of the car is 2.5 m/s2. [2 marks]
(c) Explain why the car takes a longer distance to stop on a wet road than on a dry road. [2 marks]
(d) Sketch a velocity-time graph for the car during the 4 s, assuming constant acceleration. [3 marks]
Model answer
(a) Acceleration (1)
(b) a = (v − u) ÷ t = (15 − 5) ÷ 4 (1) = 10 ÷ 4 = 2.5 m/s2 (1)
(c) There is less friction between the tyres and the road (1), so the braking force is smaller and the car slows down more slowly, so it travels further (1)
(d) Axes labelled velocity (m/s) and time (s) (1). A straight line sloping upwards, starting at 5 m/s on the velocity axis (1). The line ends at 15 m/s at 4 s, marked on the axes (1)
Exam tip
In part (b) the answer is given, so the marks are for showing the equation and the substitution. Always write one line of working before the answer.