'Explain' vs 'Describe' in GCSE Science (They Are Not the Same)

Quick answer: In GCSE science, describe means say what happens — the trend, the observation, the steps — with no reasons. Explain means say why or how it happens as a linked cause-and-effect chain, and each link in that chain is usually worth a mark. The most common way students lose marks is answering an "explain" question with a description, so the moment you read the command word, decide whether the examiner wants the what or the why.

I lost a silly number of marks in Year 10 before anyone spelled this out. I'd write a full, correct paragraph, feel pleased with it, and still drop two marks — because the question said "explain" and I'd only described. Command words aren't decoration. They're instructions, and the mark scheme is built around them. Once I started reading the command word first, before the rest of the question, my science marks stopped leaking.

I sit Cambridge IGCSE and A-Levels, but this holds identically across AQA, Edexcel and OCR GCSE — all four boards define these two words the same way, and all four mark schemes reward the same thing.

Describe = what happens, and nothing more

Describe asks you to state what you see or what happens. For a process, that's the sequence of events. For a graph, that's the trend — and the marks usually include quoting figures with units.

What describe does not want is reasons. If you write "because," you've drifted into explaining, and on a describe question that extra sentence earns nothing while costing you time.

A good describe answer for a graph will:

• state the overall trend — increases, decreases, or stays constant
• name any change in that trend — levels off, reaches a peak, then falls
• quote data with units to back it up — the "use the data" mark

Example: "Describe how the rate of reaction changes as the temperature increases. (2 marks)"

• Full marks: "As the temperature increases, the rate of reaction increases. The rate roughly doubles for every 10 degrees C rise."
• No "because," no particles, no collisions. Just what happens.

Explain = why or how, as a linked chain

Explain wants the mechanism — the reasons, connected. The examiner is hunting for a chain where each step causes the next, joined by words like so, because, therefore and this means. In most mark schemes, the number of marks quietly tells you how many links to build.

This is the part that actually changes your grade: a pile of true facts is not an explanation. "The particles have more energy. There are more collisions. The rate is faster." — three true statements, but if they're not linked, the examiner often can't award the reasoning marks. Turn the same facts into one chain and the marks appear.

A fully worked example (explain, 4 marks)

Question: "Explain, in terms of particles, why increasing the temperature increases the rate of a chemical reaction. (4 marks)"

1. Read the command word first. It says explain, so the examiner wants reasons, not "the rate goes up." And 4 marks means I'm aiming for roughly four linked points.
2. Start the chain at the cause. "As the temperature increases, the particles gain more kinetic energy and move faster." (link 1)
3. Add the next link with a connective. "Because they move faster, the particles collide more frequently." (link 2)
4. Add the energy link — the one weak answers forget. "A greater proportion of the collisions now have energy greater than or equal to the activation energy." (link 3)
5. Close the chain on the outcome. "So there are more successful collisions each second, which increases the rate of reaction." (link 4)

Read it back as one flow: faster particles, then more frequent collisions, then more collisions above the activation energy, then more successful collisions per second, and so a faster rate. Every one of those steps is a mark.

Now the same student, same knowledge, before and after:

• Before (describes, scores about 1 out of 4): "When you heat it up the particles move faster and the reaction is quicker." True — but it's a description with no mechanism. No collision frequency, no activation energy.
• After (explains, scores 4 out of 4): the linked chain above.

The facts barely changed. The connectives and the activation-energy link did.

The other command words, fast

• State / Give / Name / Identify: one word or a short phrase. No explanation, ever — don't waste time justifying it.
• Describe: what happens (covered above).
• Explain: why or how, linked (covered above).
• Compare: you must talk about both things, ideally in one sentence using "whereas" — "A is faster, whereas B is slower." Writing about only one of them can score zero.
• Suggest: apply what you know to an unfamiliar situation; there's often more than one acceptable answer. It tests whether you can transfer knowledge, not just recall it.
• Calculate / Determine: show every step of your working and put the unit on the answer — the working earns marks even if the final number is wrong.
• Evaluate: give points for and against, then a judgement or conclusion. Skipping the conclusion usually caps you below full marks.
• Justify: back a given statement with evidence or reasoning.

Mark-scheme insight most people miss: on higher-tier papers, the "explain" and "evaluate" questions carry the marks that separate a grade 7 from a grade 9. Almost anyone can state a fact. The reasoning and the linking are where the top grades actually live.

Test yourself

1. "Describe the trend shown in the graph." Should your answer include the word "because"?
2. Turn these three facts into a proper explanation: enzymes speed up reactions; at high temperature the enzyme's shape changes; the substrate no longer fits.
3. A question says "Compare aerobic and anaerobic respiration." You write two sentences, both only about aerobic respiration. What's the most you can score?

Quick answers:

1. No. Describe = what happens. "Because" belongs in an explain answer; here it earns nothing and costs you time.
2. Linked chain: "At high temperature the enzyme's shape changes — it denatures — so the substrate no longer fits the active site, which means the reaction can no longer be catalysed and the rate falls." The connectives are what earn the marks.
3. Zero — a compare question needs both things, so an answer about only one scores nothing however correct it is.

Want to know exactly which marks your wording is losing? Write a real answer and paste it into Mark my answer — it marks in your board's style and tells you whether you actually explained or just described. It's the single fastest fix I've found for command-word marks.

FAQ

How do I know if a question wants describe or explain?

Read the command word before anything else — it's almost always the first word. If it's "describe," "state" or "give," give the what. If it's "explain," "why" or "how," build the linked chain of reasons.

Are the command words the same on AQA, Edexcel, OCR and Cambridge?

Yes, in practice. All four define describe as stating what happens and explain as giving linked reasons. AQA and Cambridge both publish command-word lists that say exactly this — learn the words for one board and you've learned them for all of them.

How many points should an "explain" answer have?

Roughly match the marks: a 3-mark explain usually wants three linked points, a 4-mark one wants four. If your chain has fewer links than the marks, you're not finished yet.

Can I lose marks for writing too much?

Not directly, but you lose time — and on a describe question, extra "reasons" are wasted words that could have gone on the next answer. Answer the command word, then move on.

Two habits fixed this for me. I mark my answer on past-paper questions until "explain" automatically triggers a linked chain in my head, and I use Explain anything to see the cause-and-effect chain behind a topic so the links are ready before the exam. If a whole topic feels shaky, I turn the key "so and because" links into flashcards and drill them.

In short: describe tells the examiner what happens; explain tells them why, as a chain of linked reasons where every "so" and "because" is a mark — so read the command word first, and give the examiner the one they actually asked for.