C9: crude oils and fuels

• Cracking

  A thermal decomposition reaction
• Crude oil is a finite resource and will eventually run out
• Crude oil is used in our everyday lives for fuel, plastics, roads, and infrastructure
• Crude oil

  A black viscous (not very runny) substance that is a mixture of different hydrocarbons
• Separating crude oil into useful components

  1. Heat up crude oil to vaporize it

  2. Put vaporized crude oil into a fractionating column

  3. Different hydrocarbons condense at different temperatures and are collected
• Alkanes


  Hydrocarbons with the formula CnH2n+2
• Methane

  • Simplest alkane, saturated (all 4 carbon bonds filled)
• Drawing alkane structures

  1. Use prefixes to indicate number of carbons

  2. Draw each carbon with 4 bonds
• Combustion

  Burning of alkanes
• Complete combustion


  Burning with enough oxygen to fully oxidize the alkane into carbon dioxide and water
• Incomplete combustion

  Burning with insufficient oxygen, producing carbon monoxide, water, and carbon particles
• Catalytic converters are used to ensure complete combustion and avoid toxic carbon monoxide
• Cracking

  Breaking down large alkanes into smaller alkanes and alkenes using heat and pressure
• Alkenes


  Hydrocarbons with the formula CnH2n, have a double bond
• When decane is cracked, it produces pentane and propane as products
• The other product from cracking decane is ethene
• Homologous

  Similar compounds with similar properties
• Alkenes are more reactive than alkanes
• If you add bromine water to a solution of alkenes, the bromine water will go from brown to colourless
• Alkenes can be added together to make polymers