Hydrocarbons, Alkenes and Alkanes

• Fractional Distillation


  Used to separate crude oil into simpler, more useful mixtures
• Fractional Distillation

  1. Crude oil enters fractionating column (hot at bottom, cooler at the top)

  2. Vapours rise up column

  3. Vapours condense when they become cool enough

  4. Liquids let out of column at different heights
• Fractionating Column


  • Hot at bottom, cooler at the top
• Fractional Distillation

  • At the top - low boiling points, easy to ignite
  • At the bottom - high boiling points, hard to ignite
• Viscosity of products


  Decreases as carbon chain length decreases
• Cracking

  1. Thermal decomposition of long alkanes into shorter alkanes and alkenes

  2. Catalytic cracking - passing alkanes over hot catalyst

  3. Steam cracking - mixing alkanes with steam and heat
• Complete combustion of hydrocarbons produces carbon dioxide and water
• Incomplete combustion of hydrocarbons produces carbon monoxide
• Alkenes

  • Ethene (2-carbon)
  • Propene (3-carbon)
  • Butene (4-carbon)
  • Pentene (5-carbon)
• Alkanes


  Homologous series of saturated hydrocarbons (no double bonds)
• Crude oil is a complex mixture of hydrocarbons, formed from the remains of organisms
• Crude oil is a source of fuels, solvents and lubricants