Edexcel International A-level Chemistry: Command words and keywords

Pearson Edexcel International A-level Chemistry uses the command words defined in the specification. Mark schemes reward syllabus terminology and correct use in context. Extended questions use levels-based marking.

Command words

Command word	What to do	Common mistake
State / Name / Give	Recall; short answer	Overwriting
Define	Precise meaning	Vague
Describe	What happens; no “why”	Adding explanation
Explain	Why/how; use “because”	Only describing
Suggest	Apply to new context	Textbook recall
Calculate	Work out; show working; units	Missing working
Predict	What will happen	Unsupported
Compare	Similarities and differences	Listing separately
Evaluate	Judge; conclude with evidence	No conclusion
Deduce	Work out from information	Guess
Write	Balanced equation	Unbalanced

Keywords examiners look for

Structure and bonding

Term	Use correctly	Avoid
Electrophile	Electron-deficient	Nucleophile
Nucleophile	Electron-rich	Electrophile
Hydrogen bonding	H with N, O or F	”Strong bond”
Intermolecular forces	Between molecules	Intramolecular
Hybridisation	sp, sp², sp³	”Mixing”

Organic

Term	Use correctly	Avoid
Nucleophilic substitution	Nucleophile replaces leaving group	”Substitution”
Electrophilic addition	Electrophile adds to double bond	”Addition”
Free radical	Unpaired electron	Ion
Activation energy	Minimum for reaction	”Energy”
Catalyst	Speeds up; unchanged	”Used up”
Le Chatelier	Oppose change	”Balance”

Energetics and redox

Term	Use correctly	Avoid
Oxidation	Loss of electrons	Gain of oxygen only
Reduction	Gain of electrons	Loss of oxygen only
Oxidising agent	Accepts electrons	Reduces
Reducing agent	Donates electrons	Oxidises
Enthalpy change	ΔH	”Heat”
Exothermic	ΔH negative	”Hot”
Endothermic	ΔH positive	”Cold”
Brønsted-Lowry acid	H⁺ donor	”Sour”
Brønsted-Lowry base	H⁺ acceptor	”Bitter”
Buffer	Resists pH change	”Neutraliser”

Tips for Edexcel A-level Chemistry

1. Underline the command word before answering
2. Suggest—apply to the specific scenario
3. Show working in calculations; include units
4. State symbols in equations when asked
5. Past papers + mark schemes show acceptable wording

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Based on Pearson Edexcel International A-level Chemistry specification. Check the latest specification for your exam series.