c7 - organic chemistry

• what is crude oil?

  mixture of compounds; a fossil fuel consisting of the remains of ancient biomass

  finite resource
• what is a hydrocarbon

  a compound made up of only hydrogen and carbon atoms
• what are alkanes


  saturated hydrocarbons of a general formula CnH2n+2
• what is a homologous series?

  series of compounds with the same general formula, same functional groups and similar chemical properties
• describe the combustion of hydrocarbons

  • exothermic reaction occurring when hydrocarbons are reacted with oxygen
  • complete combustion produces carbon dioxide and water
  • incomplete combustion produces carbon or carbon monoxide and water
• describe the physical properties of alkanes

  • first few in series are gases, then change to liquids, then to solids
  • boiling points and viscosity increase as molecules get bigger
  • volatility and flammability decrease as molecules get bigger
  • poor reactivity
• explain how fractional distillation of crude oil takes place

  • crude oil is heated and vaporised
  • vapour rises up the fractionating column
  • the column is hotter at the bottom and cooler at the top
  • hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points
  • large molecules, high boiling points - collected at the bottom
  • small molecules, low boiling points - collected at the top
• what is cracking?


  when large hydrocarbons are thermally broken down into smaller and useful molecules
• what type of reaction is cracking?

  thermal decomposition
• what is an alkene?

  unsaturated hydrocarbon with general formula of CnH2n