Igcse Chemistry Revision NotesO Level Chemistry Revision Notes

Introduction To Organic Chemistry

Homologous Series:

A set of organic compounds with similar chemical properties, with a general formula and showing a gradation in physical properties as a result of increase in the size of mass of the molecule.

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The formula of each mwmber differs from the previous one by an extra –CH2 group of atom.

Members in Homologous Series have:

  • Same chemical reactions
  • Same general formula
  • Same functional group (OH – COOH)
  • Different physical property ( difference in Carbon atom, Melting point and Boiling point)

Why higher Boiling Point:

As the number of Carbon atoms increases, the intermolecular forces of attraction also increases, hence the more difficult it gets to break the molecules apart. (More heat energy is needed)

Functional Group:

An atom or group of atoms which give the molecule its characteristics properties. E.g. (C-C)


Fractional Distillation Of Crude Oil:

  • Petroleum which is a non renewable energy is a mixture of different organic compounds present in depth of soil or sea.
  • Fractional Distillation is used to separate crude oil into its components.
  • Petroleum Column is 300 m in length, therefore more efficient.

Uses of Petroleum Fractions:

Refinery Gas – Used as a fuel for cooking, heating  – portable

Gasoline/ Petrol – Fuel for car

Naphtha – Used in Petrochemical Industry, production of plastic and detergents

Kerosene / Paraffin – Jet fuel

Diesel Oil / Gas oil – Diesel engines

Lubricating Oil  – Lubricating oils , waxes and polishes

Bitumen / Ashfalt – Paving road surfaces, waterproofing material


Moving Up The Group Increase in:                           

  • Volatility
  • Ease of Ignition

Moving Down The Group  Increase in:

  • Boiling point
  • Viscosity
  • Carbon atoms in molecule

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