Fuels

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Crude oil

  • Hydrocarbons are compounds which only contain hydrogen and carbon
  • Crude oil is a complex mixture of hydrocarbons

Crude oil fractions

  • Crude oil is heated in a heater and separated into simpler, more useful mixtures. Which are:
    • Gases- used in domestic heating and cooking
    • Petrol- Used as a fuel for cars
    • Naphtha
    • Kerosene- Used as fuel for aircrafts
    • Diesel oil- Used as fuel for some cars and trains
    • Fuel oil- Used as fuel for large ships and in some power stations
    • lubricating oil
    • Bitumen- Used to surfaces roads and roofs


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Crude oil fractions and combustion

  • Hydrocarbons in different fraction differ from each other in:
    • Number of carbon an hydrogen atoms their molecules contain
    • boiling points
    • ease of ignition
    • Viscosity

Combustion

  • Complete combustion of hydrocarbons:
    • involves oxidation of the hydrocarbons
    • produces carbon dioxide and water
    • gives out energy
  • The chemical test for finding carbon dioxide is that you bubble the gas through limewater. if it turns milky then the gas is carbon dioxide
  • Word equation for the reaction when methane burns:
    •  methane + oxygen -> carbon dioxide + water
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incomplete combustion and acid rain

  • Incomplete combustion of hydrocarbons can produce carbon and carbon monoxide because there is not enough oxygen for all the carbon atoms to form carbon dioxide
  • Carbon monoxide is a toxic gas because it replace oxygen on the red blood cells
  • Problems with carbon monoxide are it is:
    • Odourless
    • colourless
    • toxic
    • lethal
  • methane + oxygen àcarbon dioxide+ carbon monoxide + carbon (soot) + water
  • Impurities in some hydrocarbon fuels result in the production of sulphur dioxide because when the fuel is burnt the sulphur reacts with oxygen from the air to form sulphur dioxide.
  • The effects of acid rain include:
    • Making rivers, lakes and soils acidic- this harms organisms living there.
    • damaging trees
    • speeding up weathering of buildings made of limestone or marble and the corrosion of metal
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climate change

  • Various gases in the atmosphere trap heat from the sun this keeps the earth warm
  • The proportion of carbon dioxide in the atmosphere varies, due to human activity.
  • Chemist are investigating the amount of carbon dioxide there is in the atmosphere by:
    • iron seeding of oceans
    • converting carbon dioxide into hydrocarbons
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Biofuels

  • Biofuels are a possible alternative to fossil fuels
  • Ethanol is a biofuel obtained by processing sugar cane or sugar beet 
  • Advantages of biofuels:
    • biofuels are renewable
    • They may help reduce the amount of carbon dioxide human activity puts into the atmosphere
    • can be carbon neutral
    • good alternatives to fossil fuels
  • Disadvantages:
    • Not carbon neutral if you account for transport and process of burning them
    • Need a lot of crops so they take up space which could be used for growing food
    • can lead to deforestation
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Biofuels

  • Biofuels are a possible alternative to fossil fuels
  • Ethanol is a biofuel obtained by processing sugar cane or sugar beet 
  • Advantages of biofuels:
    • biofuels are renewable
    • They may help reduce the amount of carbon dioxide human activity puts into the atmosphere
    • can be carbon neutral
    • good alternatives to fossil fuels
  • Disadvantages:
    • Not carbon neutral if you account for transport and process of burning them
    • Need a lot of crops so they take up space which could be used for growing food
    • can lead to deforestation
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Choosing fuels

  •  Factors that make a good fuel are :
    • it is easy to burn
    • produces a small amount of ash or smoke
    • produces a small amount of heat
    • it is easy to store and transport
  • Advantages of using hydrogen instead of petrol as fuel in cars:
    • renewable resource
  • Disadvantages:
    • Expensive
    • Not easy to buy
    • releases carbon dioxide
  • Petrol, kerosene and diesel are non-renewable resources obtained from crude oil
  • Methane is a non-renewable resource found in natural gas
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Alkanes and alkenes and cracking

  • Alkanes are saturated hydrocarbons, which are present in crude oil.
  • Alkenes are unsaturated hydrocarbons
  • If bromine water (pale yellow to red-brown in colour) is mixed with a saturated hydrocarbon it will stay the same colour. If it is mixed with and unsaturated hydrocarbon the colour fades away.
  • Cracking involves the breaking of larger alkanes into smaller, more useful ones, some of which are alkenes.
  • Cracking is necessary because there is a higher demand for smaller alkanes than what is available.
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Polymerisation

  •  Many ethene molecules can combine in a polymerisation reaction
  • The polymer formed is called polyethene
  • Other polymers can be made by combing together other monomer molecules
  • Reusing is when you use a substance more than once when it is in its original form
  • Recycling is when you change an object into something different before you use it again.
  • Some problems associated with the disposal of polymers can be overcome by recycling or by developing biodegradable polymers.
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