ORGANIC CHEMISTRY

• what is crude oil?

  • formed over millions of years from the fossilised remains of plankton
  • found in porous rocks in the crust of the earth
  • a finite resource that is used to produce fuels and other chemicals
• what are hydrocarbons?

  molecules made up of only hydrogen and carbon

  • vary in size - effects properties and how they can be used
• the larger the hydrocarbon:

  • the more viscous it is (less easily it flows)
  • the higher the boiling point is
  • the less volatile it is
  • the less easily it ignites
• how is crude oil separated?

  fractional distillation
• what does each fraction contain?

  hydrocarbons with a similar number of carbon atoms
• what are most hydrocarbons?

  alkanes
• What conditions are necessary for the formation of crude oil?

  High pressures and temperatures
• What happens to crude oil after it forms?

  It soaks into rocks and is stored
• Why is crude oil considered a finite resource?

  It takes a long time to form
• What is the first step in fractional distillation?

  Heat the oil until it turns to gas
• What happens to the gaseous mixture in fractional distillation?

  It passes into a fractionating column
• How does the temperature change in the fractionating column?

  Hot at the bottom, cooler at the top
• What happens when gases reach a lower temperature than their boiling point?

  They condense into a liquid
• Which hydrocarbons condense first in fractional distillation?

  Longest chain hydrocarbons
• What fuels are produced from shorter chain hydrocarbons?

  Diesel and petrol
• short chain hydrocarbons?

  reach the top of the column before condensing
• long chain hydrocarbons?

  lower down the column
• what is produced after fractional distillation?

  low bp - high bp

  1. refinery gases - liquified petroleum gas (LPG) / propane/butane
  2. petrol (gasoline) - fuel for cars
  3. kerosene (paraffin) - fuel for aircraft
  4. diesel - fuel for cars and trains
  5. fuel oil - generation of electricity / marine diesel engines
  6. bitumen - make roads
• what are carbons linked to?

  4 other atoms by single bonds
• what is an alkane?

  • contains one single bond
  • saturated hydrocarbon - contain the maximum number of bonds possible
  • unreactive but burn well
• examples of alkanes?

  • methane
  • ethane
  • propane
  • butane
• methane?

  • simplest alkane
  • 4 hydrogen and 1 carbon

  
• ethane?

  • 2 carbon and 6 hydrogen

  
• propane?

  • 3 carbon and 8 hydrogen atoms

  
• butane?

  • 4 carbon and 2 hydrogen atoms

  
• what do the shorter chain alkanes release?

  energy more quickly by burning meaning their is a higher demand for them as fuels
• what is combustion?

  burning
• what happens during combustion of hydrocarbon fuels?

  • both carbon and hydrogen are oxidised
  • energy is released
  • waste products are produced which are released into the atmosphere - their is a major source of atmospheric pollution
• what happens if combustion is not complete?

  • carbon monoxide, unburnt fuels and solid particles containing soot may be released
• what is carbon monoxide?

  - a colourless gas

  - an odourless gas

  - toxic gas
• what are particulates?

  solid particles in the air that can cause global dimming by reducing the amount of sunlight reaching the earths surface and cause damage to peoples lungs
• why do nitrogen and oxygen react to form nitrogen oxide?

  due to high temps reached when fuels burn
• why is nitrogen oxide bad?

  • cause respiratory problems in people
  • react with rain water to form acid rain which damages plants and buildings
• sulfur can be removed from fuels before burning (motor vehicles) and removed from waste gases after combustion (power stations)
• how are longer chain hydrocarbons broken down into shorter chain hydrocarbons?

  cracking
• what is cracking?

  an industrial process
• what are the two methods of cracking?

  steam and catalytic
• during steam cracking:

  • the hydrocarbons are mixed with steam
  • they are heated to 850 degrees
• during catalytic cracking:

  • the hydrocarbons are heated until they vaporise
  • the vapour is passed over a hot aluminium oxide catalyst
  • a thermal decomposition reaction takes place
• what are alkenes?

  Hydrocarbons with double bonds.