7 - Crude Oil

• What is the purpose of fractional distillation of crude oil?

  To separate useful substances from crude oil
• How is crude oil processed in fractional distillation?

  Crude oil is heated and fed into a fractionating column
• What happens to the temperature in the fractionating column?

  The temperature is hotter at the bottom than at the top
• Why do molecules with lower boiling points rise to the top of the column?

  They vaporize more easily than those with higher boiling points
• What occurs when vapors reach a temperature cold enough?

  They condense and change into liquid fractions
• Are the fractions collected from fractional distillation pure?

  No, they contain mixtures with similar boiling points
• What type of fractions are obtained at the bottom of the column?

  Fractions with the highest boiling points
• How do the fractions from the bottom of the column burn?

  They burn less easily with a smokier flame
• What are some uses of the fractions obtained from crude oil?

  They are used as fuels, paraffin, and diesel
• What is naphtha used for?

  To make chemicals for solvents, plastics, and other materials
• What is a hydrocarbon?

  A compound of only hydrogen and carbon
• How do fractions containing smaller molecules differ from larger ones?

  They are lighter in color, less viscous, and more volatile
• What happens to boiling points as the size of the molecules increases?

  Boiling points increase with increasing size of the molecules
• What are the trends in properties of fractions with increasing molecular size?

  • Volatility decreases with increasing size of the molecules
  • Viscosity increases with increasing size of the molecules
  • Boiling point increases with increasing size of the molecules
  • Flammability decreases with increasing size of the molecules
• What is the general formula for alkanes?

  CnH2n+2
• What type of bonds do alkanes contain?

  Only single bonds
• What is a homologous series?

  A series of compounds with the same general formula and similar chemical properties
• What is the molecular formula for methane?

  CH⁴
• What is the molecular formula for ethane?

  C²H⁶
• What is the molecular formula for propane?

  C³H⁸
• What is the molecular formula for butane?

  C⁴H¹⁰
• What is the molecular formula for pentane?

  C⁵H¹²
• What are the characteristics of a homologous series?

  • Same general formula
  • Similar chemical properties
  • Differ in physical properties such as boiling points
  • Each member differs by a CH² group
• Crude oil is composed mainly of hydrocarbons, which are molecules made up of carbon (C) and hydrogen (H).
• What is complete combustion?


  combustion where the products are carbon dioxide and water
• How is carbon monoxide toxic?


  it binds to haemoglobin in red blood cells so prevents them for carrying oxygen