chem paper 2

• Rate of reaction

  How quickly a reaction happens
• Mean rate

  The rate calculated by dividing the change in a quantity by the time, even though the rate could be changing over the time measured
• Experiment to measure rate of reaction

  1. Reacting hydrochloric acid and sodium thiosulfate in a conical flask

  2. Measuring time until solution becomes cloudy, indicating product formation

  3. Repeating at different temperatures
• As temperature increases

  The time taken for the reaction to occur decreases
• Experiment to measure rate of reaction

  1. Using a gas syringe to measure volume of gas produced

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

  3. Drawing a tangent to find rate at any point
• Ways to increase rate of reaction

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

  A reaction where the products can reform the original reactants
• Equilibrium

  The point where the rates of the forward and reverse reactions are equal, so there is no overall change
• Increasing pressure

  Favours the forward reaction in a reversible reaction
• Increasing temperature

  Favours the endothermic (reverse) reaction in a reversible reaction
• In a reversible reaction, if the forward reaction is exothermic, the reverse reaction must be endothermic, and vice versa
• Crude oil is the result of plankton being buried under water a long time ago
• Hydrocarbons

  Molecules made up of only carbon and hydrogen atoms
• Alkanes

  Hydrocarbons with single carbon-carbon bonds, with the general formula CnH2n+2
• Alkane names

  • Methane (1 carbon)
  • Ethane (2 carbons)
  • Propane (3 carbons)
  • Butane (4 carbons)
  • Pentane (5 carbons)
  • Hexane (6 carbons)
• Fractional distillation of crude oil

  1. Heating to evaporate

  2. Fractions condense at different heights in the column due to different boiling points

  3. Collecting the different fractions
• Crude oil fractions

  • LPG (gases up to 4 carbons)
  • Petrol
  • Kerosene
  • Diesel oil
  • Heavy fuel oil
  • Bitumen
• Viscosity


  The thickness or fluidity of a liquid
• Longer alkane fractions have higher viscosity
• Shorter alkane fractions are more flammable
• Alkenes

  Hydrocarbons with a carbon-carbon double bond
• Unsaturated

  Having a carbon-carbon double or triple bond
• Testing for alkenes

  Adding bromine water, which turns from orange to colourless if an alkene is present
• Cracking


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

  1. Using a zeolite catalyst at around 550°C

  2. Steam cracking at over 800°C with no catalyst
• Alcohol

  An organic compound with a hydroxyl (-OH) functional group
• Reactions of alcohols

  1. Combustion to form CO2 and H2O

  2. Reaction with sodium to form sodium alkoxide and hydrogen
• Carboxylic acid

  An organic compound with a carboxyl (-COOH) functional group
• Addition polymerisation

  Joining together monomers with a double bond
• Condensation polymerisation

  Joining together monomers with two functional groups, producing water as a by-product
• Amino acid

  An organic compound with both an amino (-NH2) and a carboxyl (-COOH) group
• DNA

  A large molecule that stores genetic code, made from two polymer strands in a double helix
• Starch

  A natural polymer made from glucose monomers
• Cellulose

  A natural polymer made from beta-glucose monomers
• Melting point and boiling point

  Tests to determine if a substance is pure
• Formulation

  A mixture designed for a specific purpose, with carefully controlled quantities of different substances
• Chromatography

  A technique for separating the components of a mixture
• DNA

  It's made from two polymers that spiral around each other in a double helix and it's made from four different monomers called nucleotides
• Starch

  A natural polymer where the monomer is glucose
• Cellulose

  A polymer that's made from beta glucose