fuels and crude oil

• what are some sources of non- renewable energy ?

  natural gas (methane), petroleum (crude oil) and coal
• why are natural gas, petroleum and coal organic compounds ?

  they all contain carbon elements as the main component in their structure
• petroleum is a mixture of hydrocarbons
• why are certain substances classified as hydrocarbons ?

  they contain only the elements hydrogen and carbon
• what makes a source of energy non- renewable ?

  they are in limited amounts and cannot be replaced quickly enough to keep up with our rate of use
• how can crude oil be separated ?

  by fractional distillation
• hydrocarbons that contain more carbon atoms have higher boiling points
• hydrocarbons that contain more carbon atoms are more viscous
• hydrocarbons that contain more carbon atoms are less flammable
• hydrocarbons that contain less carbon atoms have lower boiling points
• hydrocarbons that contain less carbon atoms are more flammable
• describe the process of separating crude oil

  1. crude oil is heated in a furnace to about 400 degrees to vapourise it
  2. the vapour passed into the fractionating column
  3. the fractions condense at different levels and are collected at the respective outlets
  4. fractions of higher boiling points condense at higher temperatures and are collected at the lower levels
  5. fractions of lower boiling points condense at lower temperatures and are collected at higher levels
• what are the fractions of crude oil ?

  • petroleum gas
  • petrol
  • naptha
  • kerosene
  • diesel
  • lubricating oil
  • bitumen
• what is petroleum gas used for ?

  fuel for cooking
• what is petrol used for ?

  fuel in cars
• what is naptha used for ?

  feedstock for making petrochemicals such as plastics and detergent
• what is diesel used for ?

  fuel for diesel engines in buses, lorries and trains
• what is kerosene used for ?

  fuel for aircraft engines, cooking using oil stoves and heating
• what is lubricating oil used for ?

  for lubricating machines and making wax and polishes
• what is bitumen for ?

  for making road surfaces and roofing
• why does the MP and BP increase down the fractions ?

  as the size of the molecule increases, the intermolecular forces of attraction between molecules increases. Hence, more energy is required to overcome the forces.
• why does the flammability decrease down the fractions ?

  as the size and mass of the molecules increase, the percentage by mass of carbon in the molecules increases so the hydrocarbons becomes less flammable
• why does the viscosity increase down the fractions ?

  as the size of the molecules increase, the intermolecular forces of attraction between molecules increase. hence, the forces are more difficult to overcome and the larger hydrocarbons become thick or waxy so they do not flow easily
• why are biofuels (eg. bioethanol) more environmentally sustainable ?

  as they come from plants in which they absorb carbon dioxide during photosynthesis, which offsets the carbon dioxide produced when the biofuel is burnt