2.5 Chemistry-Crude oil, fuels and organic chemistry

• Crude oil


  Finite resource found in rocks, formed over millions of years from the remains of an ancient biomass consisting mainly of plankton that was buried in mud
• Hydrocarbons


  Compounds that contain hydrogen and carbon atoms only
• Mixture


  2 or more elements/compounds that are not chemically combined
• Feedstock


  Raw material for an industrial process
• Fractional distillation


  1. Crude mixture is put in the bottom of the fractionating column and heated

  2. Hydrocarbons evaporate and rise up the column

  3. Cooler further up the column so hydrocarbons condense back to a liquid

  4. Each fraction contains hydrocarbons of a similar chain length and can be tapped off

  5. Mixture left at the bottom is bitumen
• Longer the hydrocarbon


  More intermolecular forces it can form so the lower its boiling point
• Shorter hydrocarbon chains


  Generally in higher demand and are more useful fuels
• As chain length increases


  • Boiling point and melting point increases
  • Viscosity increases
  • Flammability decreases
  • Volatility decreases (harder to evaporate)
  • Colour darkens
• Cracking


  Process of breaking down long chain hydrocarbons into shorter chains which are more useful
• Cracking


  1. Hydrocarbons are heated to vaporise them

  2. Vapours are passed over a hot catalyst of silica or alumina

  3. Or mixed with steam and heated to a very high temperature for thermal decomposition reactions to occur
• Thermal decomposition


  Covalent bonds break, splitting long hydrocarbons into multiple smaller ones
• Alkenes


  Unsaturated hydrocarbons with the general formula CnH2n, used as monomers to make plastics
• Cracking of decane


  Produces propene and heptane
• Economic importance of oil industry


  • Oil companies set the price of oil so have an influence globally on the economy
  • Wars or internal crisis within a country that produces oil can affect the flow of oil to other countries they sell to
• Political importance of oil industry


  • Countries that are large producers of oil can essentially cut off oil supplies to other countries; this is used as a political tool
• Social impact of oil industry


  • Supplies jobs and money for the economy
• Environmental impact of oil industry


  • Burning fossil fuels releases large amounts of carbon dioxide, a greenhouse gas, into the atmosphere, contributing towards global warming and climate change
  • Building of power stations and the process of drilling for oil causes damage to the landscape and loss of habitats
  • Oil spillages in the ocean result in the deaths of marine life and birds and are often dealt with by setting them alight
• Combustion of hydrocarbons


  1. Hydrocarbon + oxygen → carbon dioxide + water

  2. Incomplete combustion forms carbon monoxide or carbon and water
• Combustion of hydrogen


  2H2 + O2 → 2H2O
• Advantages of hydrogen as a fuel


  • No greenhouse gases are produced in the combustion of hydrogen
  • An alternative fuel option in a world where the current fuels are running out
• Disadvantages of hydrogen as a fuel


  • Hydrogen is extremely flammable
  • Most of the hydrogen produced comes from fossil fuels or electrolysis so it still has a negative impact on the environment
  • Hard fuel to store and transport, must be cooled to very low temperatures so it liquifies and can be stored and transported
• Fire triangle


  Symbol that contains the 3 things needed for a fire to burn: oxygen, fuel, heat
• Preventing and putting out fires


  1. Removal of oxygen - fire extinguishers contain carbon dioxide, fire blankets

  2. Removal of fuel - fuel resistant materials

  3. Removal of heat - water (not for electrical or oil fires)
• Calorimetry


  Experimental technique used to work out the energy released when burning a fuel
• Calorimetry method


  1. Known volume of water is added to a calorimeter and start temperature is measured

  2. Known mass of fuel is burnt beneath the calorimeter so the heat given off heats the water

  3. Maximum temperature the water reaches is recorded and the final mass of the fuel is found

  4. Energy per gram of fuel can then be calculated
• Hydrocarbons


  Contain hydrogen and carbon atoms only
• Alkanes


  Saturated hydrocarbons with the general formula CnH2n+2
• Alkenes


  Unsaturated hydrocarbons with the general formula CnH2n
• Prefixes for naming compounds


  Meth- (1C), Eth- (2C), Prop- (3C), But- (4C), Pent- (5C), Hex- (6C)
• Suffixes for naming compounds


  Alkanes - ane, Alkenes - ene, Alcohols - ol, Carboxylic acids - anoic acid
• IUPAC name


  Formal name of a compound
• Molecular formula


  Gives the number and type of each type of atom
• Structural formula


  Gives the number and type of each type of atom and their arrangement in the molecule
• Isomerism


  When 2 compounds have the same molecular formula but their structures differ
• Chain isomerism


  The main carbon chain differs in length
• Position isomerism


  In alkenes the position of double bond(s) in the molecules can differ
• Naming complex alkenes and alkanes


  1. Locate the longest unbroken chain of carbon atoms

  2. Number the carbon atoms from the end closest to a functional group or branch point

  3. Alphabetically list the functional groups attached to the carbon chain and state the carbon number the group is attached to

  4. For double bonds, count the position of the double bond by counting bonds not carbon atoms
• Isomerism


  Molecules with the same molecular formula (same number of atoms of each element) but their structures differ in some way
• Examples of isomerism


  • Chain - the main carbon chain differs in length
  • Position - in alkenes the position of double bond(s) in the molecules can differ
• Naming complex alkenes and alkanes


  1. Locate the longest unbroken chain of carbon atoms

  2. Number the carbon atoms from the end closest to a functional group or branch point

  3. Alphabetically list the functional groups attached to the carbon chain and state the carbon number the group is attached to

  4. For double bonds, count the position of the double bond by counting BONDS not carbon ATOMS

  5. If there are multiple groups of the same functional groups the prefixes di-, tri-, tetra-, penta- etc are used