Edexcel IGCSE Chemistry: Command words and keywords

Pearson Edexcel International GCSE Chemistry (4CH1) uses the command words defined in the specification. Mark schemes apply the same science-specific principles as GCSE Sciences: context and correct use of keywords matter. Recent specification updates include “Which” in the command word taxonomy.

Command words in Edexcel Chemistry 4CH1

Point-marked questions

Command word	What to do	Common mistake
State / Name / Give	Recall; short answer	Overwriting
Identify	Choose from information given	Adding explanation
Which	Select from options	Ignoring the options
Define	One precise definition	Vague or long
Write	Balanced equation; state symbols	Unbalanced or wrong products
Draw	Displayed formula; correct bonds	Wrong structure
Complete	Fill table or equation	Missing information
Calculate	Work out; show working; units	Missing units
Describe	What happens; no “why”	Adding explanation
Explain	Why or how; use “because”	Only describing
Give a reason	Say why; only the number asked	Too many reasons
Suggest	Apply to new context	Textbook recall
Predict	What will happen	Unsupported
Compare	Similarities and differences	No comparative language

Levels-based questions

Command word	What to do	Common mistake
Evaluate	Judge; conclude with evidence	No conclusion
Assess	Judge importance; conclude	Description only
Discuss	Explore aspects; conclude	One-sided
Justify	Support with evidence	Unsupported claim
Devise	Plan a method	Vague plan

Keywords examiners look for

Edexcel Chemistry mark schemes reward syllabus terminology. Keywords used incorrectly in context do not receive credit.

Structure and bonding

Term	Use correctly	Avoid
Ionic bond	Electrostatic attraction between ions	”Shared electrons”
Covalent bond	Shared pair of electrons	”Transfer” for covalent
Metallic bond	Delocalised electrons	Covalent
Ion	Charged particle	Atom
Molecule	Covalent; shared electrons	Ionic compound
Electrolyte	Conducts when molten or dissolved	Solid crystal
Delocalised	Electrons not bound to one atom	”Free” (vague)

Organic chemistry

Term	Use correctly	Avoid
Alkane	Saturated; C–C single bonds	Alkene
Alkene	Unsaturated; C=C double bond	Alkane
Ethane	C₂H₆; single bond	Ethene
Ethene	C₂H₄; double bond	Ethane
Homologous series	Same functional group; pattern	Random group
Functional group	Part determining reactions	Whole molecule
Combustion	Reaction with oxygen	Incomplete
Cracking	Breaking long chains	Wrong process
Polymerisation	Joining monomers	Depolymerisation
Addition	Single product	Substitution
Substitution	One atom replaced	Addition

Acids, bases and salts

Term	Use correctly	Avoid
Acid	H⁺ donor	”Sour”
Base	H⁺ acceptor	Alkali (for insoluble)
Alkali	Soluble base; OH⁻	Base (broader)
Neutralisation	Acid + base → salt + water	Incomplete
Salt	From acid; H⁺ replaced	Any ionic compound
Titration	Finding concentration	”Mixing”
End point	Neutralisation complete	Vague

Electrochemistry and energy

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
Exothermic	Releases energy	”Hot”
Endothermic	Takes in energy	”Cold”
Catalyst	Speeds up; unchanged	”Used up”
Activation energy	Minimum energy for reaction	Vague

Quantitative chemistry

Term	Use correctly	Avoid
Mole	6.02 × 10²³ particles	”Amount”
Relative atomic mass	Weighted mean	Mass of one atom
Concentration	mol/dm³ or g/dm³	”Strength”
Percentage yield	(actual/theoretical) × 100	Wrong formula
Limiting reactant	Runs out first	Vague

Edexcel marking principles

• Apply positively—reward what candidates show.
• Best-fit for levels-based questions.
• Context—keywords must be used correctly.
• Working—method marks even if final answer wrong.
• State symbols—(s), (l), (g), (aq) when required.

What examiner reports highlight

• Ethane vs ethene—double bond for ethene; single for ethane.
• Oxidation/reduction—wrong direction; oxidation = loss of electrons.
• Describe vs Explain—description when explanation required.
• Suggest—generic answers instead of application.
• Units—missing or wrong.
• Balanced equations—wrong stoichiometry.

Tips for Edexcel Chemistry 4CH1

1. Underline the command word before answering.
2. Learn pairs: ethane/ethene, oxidation/reduction, alkane/alkene.
3. For Suggest: Apply to the specific scenario.
4. Show working in calculations; include units.
5. State symbols in equations when asked.
6. Past papers + mark schemes show acceptable wording.

How Tutopiya helps

Tutopiya supports Edexcel IGCSE Chemistry with tutors who use the 4CH1 specification and past papers. Explore IGCSE resources or book a free trial.

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Based on Pearson Edexcel International GCSE Chemistry 4CH1 specification. Check the latest specification for your exam series.

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