chem2

• Rate of reaction


  How quickly a reaction happens
• Mean rate


  The rate could be changing over the time you measure, so this technically gives you the mean rate
• Experiment to measure rate of reaction

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

  2. Measuring the time until the solution becomes cloudy (increased turbidity)

  3. Repeating at different temperatures
• As temperature increases


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

  1. Measuring the volume of gas produced using a gas syringe

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

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

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


  Reactions where the products can return to 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 chains of single-bonded carbon atoms surrounded by hydrogen atoms
• 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 and separate the different length alkanes

  2. Collecting the fractions at different heights in the fractionating column based on their boiling points
• Fractions from fractional distillation

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


  The thickness or resistance to flow 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
• Saturated


  Having only single carbon-carbon bonds
• Testing for alkenes


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


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


  Using a temperature of around 550°C and a zeolite catalyst
• Steam cracking


  Using a temperature over 800°C with no catalyst
• Alcohols


  Organic compounds with an -OH functional group
• Reactions of alcohols


  1. Combustion to produce carbon dioxide and water

  2. Reaction with sodium to produce sodium alkoxide and hydrogen
• Carboxylic acids


  Organic compounds with a -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 acids


  Organic compounds with both an amino (-NH2) and a carboxyl (-COOH) group
• DNA


  A large molecule that stores genetic code, made from two polymers of nucleotides
• Starch and cellulose


  Natural polymers made from glucose monomers
• Formulation


  A mixture that has been specially designed to be useful for a specific purpose
• Chromatography


  A technique for separating the components of a mixture
• Polymer


  Molecules made from a large number of monomers joined together in a chain
• Nucleotides


  Four different monomers that make up DNA
• Starch


  Natural polymer where the monomer is glucose