Topic 8-Fuels ONLY

• Hydrocarbons contain carbon and hydrogen only
• crude oil is

  • A complex mixture of hydrocarbons
  • containing molecules in which carbon atoms are in chains
  • An important source of useful substance
  • A finite resource
• crude oil can be separated into simpler and more useful mixtures by fractional distillation
• ● Crude oil is a mixture of different hydrocarbons, different hydrocarbons have different boiling points

  ● The crude oil is heated in the fractionating column and the oil evaporates and condenses at several different temperatures.

  ● The fractionating column works continuously, heated crude oil is piped in at the bottom. The vaporized oil rises up the column and the various fractions are constantly tapped off at the different levels where they condense.

  ● The fractions can be processed to produce fuels and feedstock for the petrochemical industry.
• ● Gases: domestic heating and cooking

  ● Petrol: fuel for cars

  ● Kerosene: fuel for aircraft

  ● Diesel oil: fuel for some cars and trains

  ● Fuel oil: fuel for large ships and in some power stations

  ● Bitumen: surface roads and roofs
• ● Some properties of hydrocarbons depend on the size of their molecules. These properties influence their use as fuels.

  ● The shorter the molecules, the less viscous it is. (more runny) and the longer the molecules, the more viscous it is.

  ● The shorter the molecules, the lower the temperature at which that fraction evaporates or condenses – and the lower its boiling point.

  ● The shorter the molecules – the more flammable it is, so the easier it is to ignite
• in complete combustion

  ● CO2 and H2O are produced

  ● Energy is given out (exothermic)
• Incomplete combustion

  ● If there’s not enough oxygen, some of the fuel doesn’t burn Here, solid particles of soot (carbons) and unburnt fuel are released.

  ● Carbon monoxide (CO) is also released when there isn’t enough oxygen to produce CO2 instead
• ● carbon monoxide is a colourless and odourless gas which, if breathed in, prevents red blood cells carrying oxygen around your body, which leads to death
• problems with incomplete combustion

  ● Carbon monoxide causes health problems

  ● Soot causes global dimming
• impurities in some hydrocarbon fuels result in the production of sulfur dioxide

  ● Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur

  ● when the fuels are burnt in oxygen, this sulfur can react to form sulfur dioxide
• acid rain is caused when sulfur dioxide dissolves in rain water
• problems with acid rain

  ● Damages buildings and statues (made of limestone)

  ● Reduce the growth of or kill trees and crops

  ● Lower pH of water in lakes, killing fish
• ● Nitrogen and oxygen from the air combine to produce nitrogen monoxide

  ● When this nitrogen monoxide is released from vehicle exhaust systems, it combines with oxygen in the air to form nitrogen dioxide

  ● nitrogen monoxide and nitrogen dioxide are pollutants
• Advantages of Use of hydrogen fuel

  • petrol is from crude oil, a finite resource Only produces water
  • no CO2 is produced which contributes to global warming

  Disadvantages of using hydrogen fuel

  • Expensive
  • Difficult to transport and store hydrogen
  • Dangerous

  – hydrogen can be explosive
• petrol, kerosene, and diesel oil

  ● Non-renewable fossil fuels obtained from crude oil

  ● And methane is a non-renewable fossil fuel found in natural gas
• why cracking is necessary

  • Demand for smaller chained alkanes is much greater than that for longer chained alkanes
  • shorter chained hydrocarbons ignite more easily and so are more useful as fuels