What is the correct structure for a 'Compare' question?

Always state both similarities and differences. Use comparative conjunctions like 'both' for shared properties, and 'whereas' or 'however' for differences. Never write two isolated sentences that do not directly contrast the features.

GCSE Science Command Words Guide: Describe vs Explain

1. Describe vs Explain: The #1 Mark-Losing Trap

Every summer, AQA exam reports state: "Many candidates failed to score because they offered an explanation when only a description was requested, or vice versa."

Command Word: DESCRIBE

Recall / Trends / WHAT Happens

Rule: State WHAT happens or quote graph numbers. NEVER write the word "because".

When examiners ask you to "Describe a graph", they want to see: (1) General trend, (2) Any plateau or turning point, and (3) Exact paired coordinates $(x, y)$ from the graph axes with correct units.

Typical Student Error (0 Marks)

"The volume of gas increases because the magnesium particles collide more frequently with the acid particles."

Examiner Verdict: 0/2. The candidate gave collision theory (an explanation). The mark scheme for "Describe" ignores all collision theory.

Examiner Model Answer (2/2 Marks)

"The volume increases steadily from 0 to 45 cm³ in the first 60 seconds, then levels off and stays constant at 50 cm³ after 90 seconds."

Examiner Verdict: 2/2. Clear identification of initial increase, leveling off, and exact data quotes with units.

Command Word: EXPLAIN

Science Reasons / WHY or HOW

Rule: Give the scientific cause. You MUST use linking connective words like "because", "so", or "therefore".

"Explain" demands biological processes, chemical mechanisms, or physical laws. A description without a reason receives zero marks.

Typical Student Error (0 Marks)

"Explain why enzyme activity drops above 45°C."
"The line on the graph drops sharply down to zero at 60°C."

Examiner Verdict: 0/2. The candidate described the graph line rather than explaining the molecular cause.

Examiner Model Answer (2/2 Marks)

"High temperatures break bonds in the enzyme, changing the shape of the active site (denaturation) [1 mark], so the substrate no longer fits into the active site [1 mark]."

Examiner Verdict: 2/2. Connective logic clearly linking active site shape change to substrate fit.

2. State, Name & Calculate: Speed & Accuracy

These commands are designed for direct recall and mathematical execution. Do not waste precious exam time writing essays where a single word or calculation is requested.

STATE / NAME (1 Mark)

Rule: Write 1 word, a formula, or an exact value only.

Question: "Name the organelle where aerobic respiration takes place."
Correct: "Mitochondria" (takes 2 seconds).
Time-Waster: "The organelle where aerobic respiration occurs to release energy in cells is called the mitochondria." (takes 20 seconds, zero extra marks).

3. Evaluate: Conquering the 6-Mark Level Matrix

"Evaluate" questions are the gold standard of GCSE Extended Response (6-mark) questions. Examiners use a Levels of Response mark scheme rather than points-based counting.

The 6-Mark Evaluation Formula: [Advantages] + [Disadvantages] + [Justified Conclusion]

Performance Level	Marks	Examiner Criteria
Level 3 (High)	5 – 6	Balanced evaluation with relevant advantages AND disadvantages from both sides, accompanied by a clear, well-justified conclusion. Logical scientific sequencing throughout.
Level 2 (Medium)	3 – 4	Points made for both sides OR a detailed one-sided argument. Conclusion is brief or unlinked to evidence.
Level 1 (Low)	1 – 2	Isolated, simple statements without scientific detail or reasoning. No valid conclusion provided.

Examiner Secret: If you write 6 brilliant advantages of electric vehicles over petrol cars but write zero disadvantages, your mark is capped at Level 2 (maximum 4/6) regardless of how well written your answer is!

4. Compare: Similarities and Differences Linked

Command Word: COMPARE

Both • Whereas

Rule: Mention BOTH similarities and differences. Use connective words like "Both" and "Whereas".

Unlinked Sentences (1/2 Marks)

"Compare arteries and veins."
"Arteries have thick muscular walls. Veins have valves."

Verdict: 1/2. Two standalone statements. No direct comparison or similarity mentioned.

Connected Comparison (2/2 Marks)

"Both carry blood, but arteries have thick muscular walls whereas veins have thinner walls with valves to prevent backflow."

Verdict: 2/2. Direct contrast using 'whereas' and shared feature using 'both'.

5. Suggest: Applying Science to Novel Contexts

Command Word: SUGGEST

Unfamiliar Application

Rule: Apply core syllabus rules to a new scenario you have never seen before.

Students often panic and leave "Suggest" questions blank because the animal, chemical, or circuit was not in their revision notes. Examiners intentionally pick novel examples to test if you can apply core ideas (e.g. surface area to volume ratio, resistance in series, or reactivity series).

Command Word Diagnostic Quiz

Test your exam command instinct

Q1. A question asks: "Describe how the resistance of an LDR changes with light intensity." Which answer gets full marks?

Q2. On a 6-mark "Evaluate" question, a candidate writes 5 detailed advantages and NO disadvantages. What is their maximum score?

Q3. What word must you NEVER use when answering a "Describe a graph" question?

7. Frequently Asked Questions

'Describe' requires you to recall facts, state what happens, or outline patterns and graph trends using specific numbers—NEVER write 'because'. 'Explain' requires you to give scientific reasons, mechanisms, or causes using words like 'because', 'so', or 'as a result'.

Examiner mark schemes for 'Describe' questions only award marks for observational statements and quantitative graph values. Scientific theories or particle explanations are listed in the scheme under 'ignore' or 'do not credit'.

To reach Level 3 (5-6 marks), candidates must give balanced points: at least two distinct advantages, at least two distinct disadvantages, and a justified final conclusion that directly answers the question prompt based on the evidence presented.

'Suggest' means there is no single predetermined fact memorised from the syllabus. You must apply fundamental scientific principles to an unfamiliar context (e.g. an unusual organism, deep-sea submarine, or novel industrial process).