crude oil and fuels

• Combustion of hydrocarbons

  1. Requires oxygen (from the air)

  2. Burning hydrocarbons produces carbon dioxide and water
• Methane + oxygen

  Produces carbon dioxide and water
• All combustion reactions are exothermic, i.e. they release heat
• Hydrogen as a fuel

  • Used as a rocket fuel and in hydrogen fuel cells to power cars
  • Advantages: Produced from water, therefore renewable; Water is the only product of its combustion so burning hydrogen does not contribute towards global warming or acid rain
  • Disadvantages: Requires large amounts of electricity to produce hydrogen from water by electrolysis; Storage requires bulky and heavy pressurised containers; It ignites easily; Forms an explosive mixture with air
• Ethanol as a fuel

  • Advantages: Renewable; Carbon-neutral, i.e. the amount of carbon dioxide absorbed by plants during photosynthesis balances the amount of carbon dioxide released on burning the fuel made from them
  • Disadvantages: Dependent on climate for sugar growth; Decreases the amount of land available to grow food crops - could result in higher food prices
• Fire triangle

  Factors required for combustion to occur
• Firefighting and fire prevention

  Removing one or more factors from the fire triangle: Oxygen (using carbon dioxide and fire blankets), Heat (using water), Fuel (felling trees in a forest fire)
• Hydrocarbons

  Compounds that contain carbon and hydrogen atoms only; Carbon atoms have the ability to form bonds with other carbon atoms resulting in the formation of hydrocarbon chains; Longer chains have higher boiling points
• Crude oil

  Complex mixture of hydrocarbons, produced from the remains of dead marine animals and plants that lived around 300 million years ago; Formed by pressure and heat breaking down the remains
• Fractional distillation of crude oil

  Crude oil is boiled/vaporised before it enters the fractionating column; Hydrocarbons condense at different heights in the column based on their boiling points; Lower boiling point compounds are collected higher in the column
• Fractions from fractional distillation

  • Refinery gases
  • Petrol
  • Naptha
  • Paraffin (kerosine)
  • Diesel oil (gas oil)
  • Lubricating oil
  • Bitumen
• Intermolecular forces


  Larger hydrocarbon molecules have more intermolecular forces, requiring more energy to overcome them for melting or boiling; Explains why longer chain hydrocarbons are more viscous
• The fire triangle shows the factors required for combustion to occur: heat, fuel, oxygen