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
• Increasing temperature


  Decreases the time taken for the reaction
• 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 in solution
  • 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


  A mixture of hydrocarbons formed from buried plankton
• Alkanes


  Hydrocarbons with single-bonded carbon atoms in a chain
• Fractional distillation of crude oil

  1. Heating to evaporate and separate into fractions based on boiling point

  2. Longer alkanes have higher boiling points and condense lower in the column
• Crude oil fractions


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


  1. Using a zeolite catalyst at around 550°C

  2. Steam cracking uses even higher temperatures over 800°C without a catalyst
• Alcohols


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


  1. Combustion to produce CO2 and H2O

  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 double bonds
• Condensation polymerisation


  Joining together monomers with two functional groups, producing water
• 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 polymer strands in a double helix
• Starch and cellulose


  Natural polymers made from glucose monomers
• Melting point and boiling point


  Tests to determine if a substance is pure
• Formulation


  A mixture designed for a specific purpose with specific quantities of ingredients
• Chromatography


  A technique to separate 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
• Cellulose


  Polymer made from beta glucose
• Proteins


  Polymers made from amino acid monomers
• Melting point/Boiling point


  Way to tell if a substance is pure - should be a very specific temperature