organic

• Products produced from crude oil

  • Plastics
  • Petrol
  • Pharmaceuticals
  • Cosmetics
• Crude oil is a finite resource
• Crude oil is formed over millions of years from the remains of tiny sea creatures called plankton
• Molecules found in crude oil

  • Hydrocarbons
• Hydrocarbon


  Molecules made up of hydrogen and carbon atoms only
• Hydrocarbon


  • Methane
• Methane

  Formula: CH4, contains one carbon atom covalently bonded to four hydrogen atoms
• Alkanes

  Hydrocarbons like methane and ethane
• Alkanes


  • General formula: CnH2n+2
• Calculating hydrogen atoms in alkanes

  Multiply the number of carbon atoms by 2 and then add 2
• Propane is an alkane with three carbon atoms
• Butane is an alkane with four carbon atoms
• Alkanes are saturated molecules because the carbon atoms are fully bonded to hydrogen atoms
• Properties of hydrocarbons depend on the size of their molecules


  1. Viscosity

  2. Flammability

  3. Boiling point
• First four alkanes

  • Methane
  • Ethane
  • Propane
  • Butane
• Viscosity

  • Thickness of a fluid, high viscosity means slow flow, long-chain hydrocarbons are extremely viscous
• Flammability

  • How easily a hydrocarbon combusts, short-chain hydrocarbons are extremely flammable, long-chain hydrocarbons are difficult to burn
• Boiling point

  • Temperature at which a liquid turns to a gas, short-chain hydrocarbons have low boiling points and are gases at room temperature, long-chain hydrocarbons have high boiling points
• Short-chain hydrocarbons are gases at room temperature
• As the size of hydrocarbon molecules increases

  Viscosity increases, flammability decreases, boiling point increases
• How hydrocarbons can be used as fuels

  1. Hydrocarbons are used as fuels in ships, planes, cars, and various other cases

  2. Short chain hydrocarbons are highly flammable with low boiling points, while larger molecules are less flammable with higher boiling points and higher viscosity
• Hydrocarbon fuels release energy when combusted
• During combustion, carbon and hydrogen atoms in the fuel react with oxygen, leading to oxidation of carbon and hydrogen
• Complete combustion of hydrocarbons with unlimited oxygen produces carbon dioxide and water
• How to write chemical equations for complete combustion

  Balance the carbon atoms first, then balance the hydrogen atoms, and finally balance the oxygen atoms
• Example of balanced equation for complete combustion of methane

  • CH4 + 2O2 -> CO2 + 2H2O
• Example of balanced equation for complete combustion (practice)

  • 3C3H8 + 5O2 -> 3CO2 + 4H2O
• Fractional distillation

  1. Crude oil is separated into fractions containing hydrocarbons with a similar number of carbon atoms

  2. Crude oil is heated to a very high temperature causing it to boil and all hydrocarbons to evaporate and turn into a gas

  3. Crude oil vapors are fed into the fractional distillation column

  4. The column is hotter at the bottom and cooler at the top

  5. Hydrocarbon vapors rise up the column

  6. Hydrocarbons condense when they reach their boiling points and turn back into a liquid

  7. Liquid fractions are removed

  8. Remaining hydrocarbons continue moving up the column and condense when they reach their boiling points

  9. Long-chain hydrocarbons with high boiling points are removed from the bottom of the column

  10. Short-chain hydrocarbons with low boiling points do not condense and are removed from the top of the column as gases
• Examples of fractions produced by fractional distillation

  • Petrol
  • Diesel
  • Kerosene
  • Heavy fuel oil
  • Liquefied petroleum gas
• Some fractions produced by fractional distillation are used as fuels
• Some fractions produced by fractional distillation are used as feedstock for the petrochemical industry
• Feedstock is a chemical used to make other chemicals
• You can find questions on fractional distillation in the vision workbook
• Cracking


  Breaking down a long chain alkane to produce smaller, more useful molecules
• Alkanes

  • General formula: CnH2n+2
  • Single covalent bonds between carbon atoms
• Long chain hydrocarbons are not very flammable and do not make good fuels
• Shorter chain alkanes are used for fuels, for example in cars
• Cracking produces shorter chain alkanes and alkenes
• Alkenes

  • Double covalent bond between two carbon atoms
  • More reactive than alkanes
• Alkenes are used to make chemicals called polymers and as starting materials for other useful chemicals