You are viewing a free preview of this lesson.
Subscribe to unlock all 10 lessons in this course and every other course on LearningBro.
Every exam question begins with a command word — the instruction that tells you exactly what the examiner wants. Misreading or misunderstanding the command word is one of the most common reasons students lose marks. You might know the chemistry perfectly but still score zero if you describe when the question asks you to explain.
This lesson covers every command word used in the Edexcel GCSE Chemistry specification, with Chemistry-specific examples and the mistakes students commonly make.
The command word determines:
A question worth 3 marks starting with "State" requires three short facts. The same 3-mark question starting with "Explain" requires reasons and logical links.
Exam tip: Before writing anything, underline the command word. Ask yourself: "What is this word telling me to do?" This takes 5 seconds and can save you from throwing away marks.
What it means: Write a short, factual answer. No explanation is needed.
How to answer: Keep it brief. One word, one phrase, or one sentence per mark.
| Question | Good Answer |
|---|---|
| "State the number of protons in a sodium atom." | 11 |
| "Give the formula for sulfuric acid." | H₂SO₄ |
| "Name the product when magnesium reacts with hydrochloric acid." | Magnesium chloride (and hydrogen) |
Writing too much. If the question says "State," you do not need to explain. Extra information wastes time and can sometimes introduce errors that cost marks.
What it means: Say what happens. Give an account of the process, observations, or pattern. No explanation of why is needed.
How to answer: Focus on what happens, in a logical order. Use specific chemistry terminology.
| Question | Good Answer |
|---|---|
| "Describe the trend in reactivity of Group 1 metals." | "Reactivity increases as you go down Group 1. Lithium is the least reactive; caesium is the most reactive." |
| "Describe what you would observe when sodium is added to water." | "The sodium floats on the surface, moves around rapidly, fizzes, and melts into a silvery ball. The sodium gets smaller and eventually disappears." |
Explaining why something happens. If the question says "Describe the trend," do not explain it in terms of electron shells. Save that for "Explain" questions.
Exam tip: "Describe" = WHAT happens. "Explain" = WHY it happens. Keeping this distinction clear in your mind is worth several marks across both papers.
What it means: Give reasons. Say why something happens using scientific knowledge. Use cause-and-effect language.
How to answer: Use linking words such as "because," "therefore," "this means that," and "as a result."
| Question | Good Answer |
|---|---|
| "Explain why sodium is more reactive than lithium." | "Sodium has more electron shells than lithium, so its outer electron is further from the nucleus. The electrostatic attraction between the nucleus and the outer electron is weaker, therefore the outer electron is lost more easily. This makes sodium more reactive." |
| "Explain why ionic compounds conduct electricity when molten but not when solid." | "In the solid state, the ions are held in a fixed lattice and cannot move. When molten, the ions are free to move and can carry charge through the liquid, so an electric current can flow." |
Describing instead of explaining. Writing "sodium is more reactive because it is lower in the group" is not an explanation — it just restates the pattern. You must explain the mechanism (electron shells, nuclear attraction, ease of electron loss).
What it means: Identify both similarities and differences. You must do both.
How to answer: Use comparative language: "whereas," "both," "however," "in contrast," "similarly."
| Question | Good Answer |
|---|---|
| "Compare the bonding in sodium chloride and diamond." | "Both sodium chloride and diamond have strong bonding throughout their structures. However, sodium chloride has ionic bonds formed by the transfer of electrons from sodium to chlorine, whereas diamond has covalent bonds formed by the sharing of electrons between carbon atoms. Both have high melting points, but sodium chloride conducts electricity when molten whereas diamond does not conduct electricity." |
Only giving differences. "Compare" requires both similarities and differences. Another mistake is writing about each substance separately without linking them — always use comparative words.
What it means: Apply your knowledge to an unfamiliar context. There may not be a single correct answer — the examiner wants to see logical scientific reasoning.
How to answer: Use your existing knowledge and apply it to the new situation. Be specific and justify your reasoning.
| Question | Good Answer |
|---|---|
| "A student finds that reaction X is faster at 40°C than at 20°C. Suggest why." | "At 40°C the particles have more kinetic energy, so they move faster. This means there are more frequent collisions and a greater proportion of collisions have energy equal to or greater than the activation energy, so the rate of successful collisions increases." |
Being too vague. "It is hotter so it goes faster" is not sufficient. Suggest questions still require scientific reasoning and terminology.
Exam tip: "Suggest" questions often use unfamiliar contexts, but the underlying chemistry is always from the specification. Do not panic — identify which topic is being tested and apply your knowledge.
What it means: Work out a numerical answer using mathematics. You must show your working.
How to answer: Write the formula, substitute the values, show each step, give the final answer with correct units.
| Question | Good Answer |
|---|---|
| "Calculate the relative formula mass (Mr) of calcium carbonate (CaCO₃)." | "Mr = 40 + 12 + (16 × 3) = 40 + 12 + 48 = 100" |
Not showing working. Even if your final answer is correct, a calculation question with no working shown typically earns fewer marks. If your final answer is wrong but your method is correct, you can still earn method marks — but only if the examiner can see your working.
Subscribe to continue reading
Get full access to this lesson and all 10 lessons in this course.