Alkanes and alkenes both belong to homologous series. Describe four features of a homologous series.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. All members contain the same functional group or general formula.
2. They exhibit similar chemical properties.
3. Each successive member differs by one CH₂ unit.
4. Physical properties such as boiling point or viscosity change gradually with increasing carbon number.
2. They exhibit similar chemical properties.
3. Each successive member differs by one CH₂ unit.
4. Physical properties such as boiling point or viscosity change gradually with increasing carbon number.
Examiner tips
- Use the command word ‘describe’ – list the four features clearly. Include the key phrases from the mark scheme (functional group, CH₂ unit, gradual trend).
- Show the features as separate points to avoid missing any.
Mark scheme (4 marks)
- Members of a homologous series share the same functional group / general formula
- Members have similar chemical properties
- Each successive member differs by one CH₂ unit
- Physical properties (such as boiling point or viscosity) show a gradual trend / change gradually as the number of carbon atoms increases
Key terms in this question
Related
- All Pearson Edexcel International GCSE Chemistry (4CH1) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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