C2 revision

• 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 point
• 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
• Activation energy


  The energy needed for particles to collide successfully and react
• 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
• Crude oil


  A mixture of hydrocarbons formed from buried plankton
• Alkanes


  • Molecules made up of only carbon and hydrogen, with a general formula of CnH2n+2
  • The shortest alkanes are gases, the longest are liquids
• 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
• LPG


  The lightest fraction of crude oil, containing alkanes up to 4 carbons long
• Alkenes


  Hydrocarbons with a carbon-carbon double bond, making them unsaturated
• Bromine water test


  Used to test for the presence of an alkene, which will decolourise the orange bromine water
• Cracking


  Breaking down longer alkanes into shorter alkanes and alkenes using high temperature and/or a catalyst
• Alcohols


  Organic compounds with a hydroxyl (OH) functional group
• Carboxylic acids


  Organic compounds with a carboxyl (COOH) functional group
• Condensation polymerisation


  Joining monomers with two functional groups (e.g. alcohol and carboxylic acid) to form a polymer, releasing water
• Amino acids


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


  A large molecule that stores genetic information, made up of two polymer strands in a double helix
• Purity


  Determined by measuring the melting point or boiling point, which should be a specific temperature for a pure substance
• 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
• Double helix


  Made from two polymers that spiral around each other
• Nucleotides


  Four different monomers that make up DNA
• Starch


  Natural polymer where the monomer is glucose
• Cellulose


  Polymer made from beta glucose
• Proteins


  Monomers are amino acids
• Melting point/Boiling point


  Way to tell if a substance is pure
• Formulation


  Mixture that has been specially designed to be useful in a very specific way with very specific quantities of different substances
• Chromatography


  1. Separating substances in a mixture

  2. Stationary phase (often special chromatography paper or filter paper)

  3. Mobile phase (often just water) rises up the paper due to capillary action

  4. Draw line at bottom in pencil

  5. Measure how far solvent and substances have moved to calculate RF value
• RF value is a ratio of how far a spot has moved compared to the solvent, between 0 and 1
• RF values can be compared to known values to identify substances in a mixture
• Testing for hydrogen


  Hold burning splint over test tube, produces squeaky pop
• Testing for oxygen


  Relight glowing splint
• Testing for carbon dioxide

  Bubble through lime water, turns cloudy