CC16-17 (fuels and the atmosphere)

• hydrocarbons: a compound containing ONLY hydrogen and carbon atoms
• crude oil: a thick brown liquid that is a mixture of hydrocarbons found in deposits underground
• molecules in crude oil: hydrocarbons with carbons added in into both chain-and-ring-shaped molecules
• crude oil is a finite resource (there is a limited amount)
• fractional distilation: a type of distillation used to seperate mixtures of 2 or more liquids
• fractional distillation seperates compounds according to their boiling points
• crude oil is heated to nearly 400 degrees celcius to become nearly a full gas
• fractionating columns: hot gas rises up and different parts condense as it cools
• main fractuions of crude oil: petrol, diesel oil, fuel oil, kerosene and bitumen
• viscosity: how easy fluids flow. higher viscosity= runnier
• kerosene is a fuel for aircraft
• bitumen is used for surfacing roads and roofs
• homologous series : a family of closely related compounds with molecular formulae that differ only in the number of 'CH2'
• alkanes are hydrocarbons containing only single bonds (names end with 'ane'
• first 3 alkanes : Methane- CH4

  Ethane-C2H6

  Propane-C3H8
• combustion is when a compound reacts with oxygen, producing a flame
• complete combustion is combustion that produces only water and carbon dioxide and releases the most energy
• complete combustion equation:

  fuel+oxygen->carbon dioxide +water
• incomplete combustion is combustion that produces a mixture of carbon dioxide, carbon monoxide, carbon and water(produces less energy)
• icomplete combustion happens when there is not enough oxygen for all of the reactants to be fully oxidised
• Carbon monoxide is a colourless gass that is highly toxic
• carbon monoxide sticks to haemoglobin in the blood which prevents it from carrying oxygen ( how it kills you)
• soot is small particles of carbon produced by incomplete combustion
• problems with soot : -blackens and dirties buildings

  -causes lung problems when breathed in
• how to prevent incomplete combustion:

  • boilers need good air supply
  • boiler flue pipe needs to be checked for blockages every year
• sulfur is an impurity that is naturally present in small amounts of oil and coal
• acid rain has a pH lower than 5.2
• acid rain forms when sulfur dioxide dissolves in water in clouds to form sulfurous acid (H2SO3)which oxidises to become sulfuric acid(H2SO4)
• effects of acid rain:

  • soil becomes too acidic for crops
  • acid in rivers can kill fish
  • acid rain increases corrosion of limestone,which damages buildings and statues
• nitrogen oxides are gases formed at high temperatures inside internal combustion engines
• problems of nitrogen oxides:

  • dissolves in clouds, forming acid rain
  • NO2 causes lung damage
  • NOx can cause smog to form
• cracking: breaking downlonger, less useful hydrocarbons into smaller, more useful ones
• cracking hydrocarbons: heat hydrocarbons and pass the vapours over an aluminium oxide catalyst heated to 650 degrees celcius
• products of cracking an alkane :

  an Alkane and an Alkene
• alkenes are hydrocarbons containing a C=C double bond
• there is more demand for shorter hydrocarbons (eg. petrol and gas)than longeer ones (bitumen) cracking turns the longer ones into shorter ones
• hydrogen has the potential to be used as fuel for cars
• advantages of hydrogen as a fuel:

  • only produces H2O when burnt so doesnt contribute to global warming
  • can be produced with renewable energy
• disadvantagesof hydrogen as a fuel:

  • it is currently produced in ways that produce CO2 which contributes to global warming
  • its difficult to store
• early earth: 4.5-3.5 billion years ago the earth was extremely hot and there were many volcanoes