AQA - chemistry paper 2

• Rate of reaction

  How quickly a reaction happens
• Measuring rate of reaction

  1. Reacting hydrochloric acid and sodium thiosulfate

  2. Measuring time until solution becomes cloudy

  3. Repeating at different temperatures
• Increasing temperature

  Decreases time taken for reaction
• Measuring rate of reaction

  1. Using gas syringe to measure volume of gas produced

  2. Plotting graph with quantity on y-axis and time on x-axis
• Tangent on graph

  Used to find rate at any time
• Factors that increase rate of reaction

  • Increasing concentration of reactants
  • Increasing pressure of gas reactants
  • Increasing surface area of solid reactants
  • Increasing temperature
  • Adding a catalyst
• Catalyst

  Reduces activation energy, increases likelihood of successful collisions
• Reversible reaction


  Reaction where products can reform reactants
• Equilibrium

  Point where forward and reverse reaction rates are equal, no overall change
• Increasing pressure

  Favours forward reaction in equilibrium
• Increasing temperature

  Favours endothermic (reverse) reaction in equilibrium
• In a reversible reaction, if forward is exothermic, reverse is endothermic and vice versa
• Crude oil

  Result of plankton being buried under water, consists mostly of hydrocarbons
• Alkanes

  Hydrocarbons with single-bonded carbon chains
• Alkane names

  • Methane
  • Ethane
  • Propane
  • Butane
  • Pentane
  • Hexane
• Fractional distillation of crude oil

  1. Heating to evaporate

  2. Fractions condense at different heights based on boiling points
• Crude oil fractions

  • LPG
  • Petrol
  • Kerosene
  • Diesel
  • Heavy fuel oil
• Viscosity

  Measure of thickness/resistance to flow
• Longer alkane fractions have higher viscosity
• Shorter alkane fractions are more flammable
• Alkenes

  Hydrocarbons with carbon-carbon double bonds
• Unsaturated

  Having a carbon-carbon double bond
• Testing for alkenes

  Adding bromine water, solution turns colourless
• Cracking

  Breaking down longer alkanes into shorter alkanes and alkenes
• Catalytic cracking

  Using high temperature (550°C) and zeolite catalyst
• Steam cracking

  Using very high temperature (over 800°C) without catalyst
• Alcohols


  Organic compounds with -OH functional group
• Combustion of alcohols

  1. Complete: CO2 and H2O

  2. Incomplete: CO and H2O
• Reaction of alcohols with sodium

  Produces sodium alkoxide and hydrogen
• Carboxylic acids


  Organic compounds with -COOH functional group
• Addition polymerisation


  Joining together monomers with double bonds
• Condensation polymerisation


  Joining together monomers with two functional groups, producing water
• Amino acids

  Contain both amino (-NH2) and carboxyl (-COOH) groups
• DNA

  Double-helix polymer made from nucleotide monomers
• Starch


  Natural polymer made from glucose monomers
• Cellulose


  Natural polymer made from beta-glucose monomers
• Melting/boiling point


  Used to test purity of substances
• Formulation

  Mixture with specific quantities of substances for a purpose
• Chromatography


  Technique to separate substances in a mixture
• Double helix


  Made from two polymers that spiral around each other