Chemical bonds and types of bonding

• Crude oil is a finite resource found in rocks
• Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
• Mixture


  2 or more elements that are not chemically combined
• The chemical properties of each substance in the mixture are unchanged
• Separating substances in crude oil mixture

  Physical methods including distillation
• Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon only (hydrocarbons)
• Most of these saturated hydrocarbons are alkanes
• Hydrocarbons

  Have the general formula: CnH2n+2

  
• First 4 alkanes

  • Methane
  • Ethane
  • Propane
  • Butane

  
• Fractional distillation

  Oil is heated in the fractionating column and the oil evaporates and condenses at different temperatures
• The many hydrocarbons in crude oil can be separated into fractions each of which contains molecules with a similar number of carbon atoms
• The fractionating column works continuously, with heated crude oil piped in at the bottom
• The vaporised oil evaporates and rises up the column and the various fractions are constantly tapped off at the different levels where they condense
• Fuels produced from crude oil fractions

  • Petrol
  • Diesel oil
  • Kerosene
  • Heavy fuel oil
  • Liquefied petroleum gases
• Materials produced by the petrochemical industry

  • Solvents
  • Lubricants
  • Polymers
  • Detergents
• The vast array of natural and synthetic carbon compounds occur due to the ability of carbon atoms to form families of similar compounds
• Viscosity


  How runny a hydrocarbon is
• Alkenes


  Hydrocarbons with the functional group C=C

  
• Shorter the hydrocarbon molecules

  Less viscous it is
• First 4 alkenes


  • Ethene
  • Propene
  • Butene
  • Pentene

  
• Longer the hydrocarbon molecules

  More viscous it is
• Shorter the hydrocarbon molecules


  Lower the temperature at which that fraction is vaporised or condensed, and the lower its boiling point
• Unsaturated carbons


  • Can be represented in the following forms:
• Shorter the hydrocarbon molecules

  More flammable it is
• Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion (meaning carbon or carbon monoxide is formed (CO))
• Burning hydrocarbons as fuel

  1. Hydrocarbon -> carbon dioxide + water

  2. Hydrogen and carbon are oxidised in the reaction
• Reactions of alkenes


  1. React with hydrogen

  2. React with water

  3. React with halogens

  
• Cracking hydrocarbons


  1. Passing them over a hot catalyst (catalytic cracking)

  2. Mixing them with steam and heating to a very high temperature so that thermal decomposition reactions can occur (steam cracking)
• In reactions with hydrogen, water and halogens

  • The C=C bond is broken to form a C-C bond
  • The compound added splits into two groups and the two groups are added to the 2 different carbons in the C=C bond (each group can be added to either carbon)
  • H2 splits into 2 H's, H2O splits into a H and an OH, Br2 splits into 2 Br's (same for Cl2 or I2)
• Alkenes


  Unsaturated hydrocarbons produced by cracking, with the general formula CnH2n and at least one double carbon-carbon bond

  
• Alcohols


  Contain the functional group -OH

  
• First 2 alkenes


  • Ethene
  • Propene

  
• First 4 alcohols


  • Methanol
  • Ethanol
  • Propanol
  • Butanol

  
• Alkenes react with bromine water, turning it from orange to colourless, while alkanes do not

  
• Alkenes are used for producing other chemicals (e.g. polymers)
• Alcohols can be represented by:
• Some of the products made from cracking are useful as fuels, since they have shorter chains than the alkanes you started with, making them more flammable so a better fuel
• Alcohols burn in air, which produces carbon dioxide and water
• Cracking reaction equation


  1. You must make sure there are the same number of carbons and hydrogens on each side of the equation

  2. Going from a bigger molecule to usually 2 smaller molecules
• Alcohols dissolve in water to form a neutral solution (has a pH of 7)