Specification Point 4.1:
Know that a hydrocarbon is a compound of hydrogen and carbon only


Crude oil: A mixture of hydrocarbons.

  • Hydrocarbon: Compound that contains only hydrogen and carbon atoms
  • Example:

The-first-three-Alkanes table, IGCSE & GCSE Chemistry revision notes

Diagram showing the hydrocarbons methane, ethane and propane

Specification Point 4.2:
Understand how to represent organic molecules using empirical formulae, molecular formulae, general formulae, structural formulae and displayed formulae

Representing Organic Molecules


Organic molecule definitions table, IGCSE & GCSE Chemistry revision notes

Example: Ethane (C2H6)

Specification Point 4.3:
Know what is meant by the terms homologous series, functional group and isomerism

Representing Organic Molecules

  • Homologous series: A series of organic compounds that has similar features:
    • Same general formula
    • Same functional group
    • Similar chemical reactions
    • Physical properties show graduations
    • Each member differs in molecular formula from the next by CH2
  • Functional group: A group of atoms bonded in a specific arrangement that controls the property of the homologous series:

  • Isomerism: Compounds that have the same molecular formula but different structural formulae

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.