Chemistry Spec

• Mean rate of reaction

  Quantity of reactant used & time taken
• Mean rate of reaction

  Quantity of product formed & time taken
• Factors which affect the rates of chemical reactions

  • Concentration of reactants
  • Pressure of reacting gases
  • Surface area of solid reactants
  • Temperature
  • Presence of catalyst
• Collision theory


  1. Reacting particles collide with each other

  2. Reacting particles have sufficient energy
• Activation energy


  Minimum energy particles need in order to react
• Increasing the concentration of reactants in solution, the pressure of reacting gases, the surface area of solid reactants

  Increases the frequency of collisions and so increases the rate of reaction
• Increasing the temperature

  Increases the frequency of collisions and makes the collisions more energetic, so increases the rate of reaction
• Catalysts

  Increase the rate of reaction by providing a different pathway for the reaction that has a lower activation energy
• Reversible reactions

  The products can react to produce the original reactants
• Equilibrium

  The forward and backward reactions of a reversible reaction occur at the same rate within a closed system
• Le Chatelier's principle

  If a reaction is at equilibrium and a change is made, the reaction responds to counteract the change
• If the concentration of a reactant is increased

  More products will be formed, until equilibrium is reached again
• If the concentration of a product is decreased

  More reactants will form, until equilibrium is reached again
• If the temperature of a system at equilibrium is increased

  The relative amount of products increases for an endothermic reaction
• If the temperature of a system at equilibrium is increased

  The relative amount of products decreases for an exothermic reaction
• For gases, increasing the pressure

  Causes the equilibrium position to shift towards the side with the smaller number of molecules
• For gases, decreasing the pressure

  Causes the equilibrium position to shift towards the side with the larger number of molecules
• Crude oil is a finite resource found in rocks formed from the remains of an ancient biomass consisting mainly of plankton that was buried in mud
• Crude oil


  A mixture of a very large number of compounds, mainly hydrocarbons which are mostly alkanes
• Hydrocarbon

  A compound which contains hydrogen and carbon only
• First four alkanes

  • Methane, ethane, propane, butane
• Fractional distillation of crude oil

  1. Separates it into fractions with similar number of carbon atoms

  2. These fractions can be processed to provide fuels and feedstocks for the petrochemical industry
• Fuels separated from crude oil

  • Petrol, diesel, kerosene, heavy fuel oil, liquefied petroleum gas
• Products of the petrochemical industry


  • Solvents, lubricants, polymers, detergents
• Boiling point, viscosity and flammability of hydrocarbons

  Depend on the size of their molecules
• Combustion of hydrocarbon fuels releases energy and the carbon and hydrogen in the fuels are oxidised, and in complete combustion carbon dioxide and water are produced
• Cracking of hydrocarbons


  1. Produces smaller, more useful molecules

  2. The two types are catalytic cracking and steam cracking
• Cracking produces alkanes and alkenes
• Alkenes


  Hydrocarbons with a double carbon-carbon bond, more reactive than alkanes
• Alkenes


  React with bromine, turning orange bromine water colourless
• Alkenes


  Are unsaturated because they contain two fewer hydrogen atoms than the alkane with the same number of carbon atoms
• First four alkenes


  • Ethene, propene, butene, pentene
• Alkenes burn in air with smoky flames due to incomplete combustion
• Reactions of alkenes

  With hydrogen, water and halogens by addition across the carbon-carbon double bond
• Alcohols


  Contain the functional group -OH
• Aqueous solutions of ethanol are produced when sugar solutions are fermented using yeast
• Carboxylic acids


  Have the functional group -COOH
• First four carboxylic acids


  • Methanoic acid, ethanoic acid, propanoic acid, butanoic acid
• Addition polymerisation


  Monomers join together to form polymers, and the carbon-carbon double bond is turned into a carbon-carbon single bond
• Condensation polymerisation


  Monomers with two functional groups react and join together, usually losing small molecules such as water