topic c7- organic chemistry

• hydrocarbon examples

  
• hydrocarbons

  • only contain hydrogen and carbon atoms
  • alkanes are the simplest type of hydrocarbon
  • alkanes all have C-C single bonds
• alkanes

  • are homologous series- group of organic compounds that react in a similar way
  • are unsaturated compounds- each C atom forms 4 single covalent bonds
• hydrocarbon properties change as the chain becomes longer

  • boiling point decreases
  • flammability decreases
  • viscosity increases (how runny it is)
• general formula

  CnH2n+2
• combustion

  exothermic
• complete combustion

  an oxidation reaction that occurs when a fuel reacts with plenty of oxygen
• combustion

  hydrocarbon + oxygen -> carbon dioxide + water (+energy)
• combustion

  • hydrocarbons are used as fuels because combustion releases lots of energy
  • alkanes
• fuels

  • a substance that releases heat when burnt
• fractional distillation

  • a process used to separate the hydrocarbons in crude oil into fractions according to their boiling points
• crude oil

  • a mixture of many hydrocarbons
  • fossil fuel
  • it's a finite resource found in rocks and formed from dead plants (plankton) and animals that have spent millions of years buried in mud
• crude oil is processed to produce fuels and to provide stock chemicals used to manufacture polymers, solvents, detergents + lubricants
• fractional distillation

  • hot at bottom
  • cold at top
  • evaporation
  • condensation
• fractional distillation

  
• cracking of crude oil

  thermal decomposition reaction
• cracking of crude oil

  • splitting up of long-chain hydrocarbons, into shorter more useful ones (hydrocarbons)
  • shorter- lower melting + boiling points, more flammable + volatile
• cracking of crude oil

  long-chain alkane -> shorter-chain alkane + alkene
• alkene

  are hydrocarbons with a double bond between 2 carbon atoms (unsaturated)
• two methods of cracking

  • catalytic
  • steam
• catalytic cracking

  hydrocarbon vapour is passed over a hot powdered aluminium catalyst
• steam cracking

  hydrocarbon vapour is mixed with steam and heated to a very high temperature