CHEMISTRY

• MS 1a


  • Recognise and use expressions in decimal form
• MS 1c


  • Use ratios, fractions and percentages
• MS 1d


  • Make estimates of the results of simple calculations
• MS 4a


  • Translate information between graphical and numeric form
• MS 4b


  • Drawing and interpreting appropriate graphs from data to determine rate of reaction
• MS 4c


  • Plot two variables from experimental or other data
• MS 4d


  • Determine the slope and intercept of a linear graph
• MS 4e


  • Draw and use the slope of a tangent to a curve as a measure of rate of change
• Factors which affect the rates of chemical reactions include: the concentrations of reactants in solution, the pressure of reacting gases, the surface area of solid reactants, the temperature and the presence of catalysts
• Students should be able to

  Recall how changing these factors affect the rate of chemical reactions
• pH


  Measure of rate of reaction at a specific time
• MS 1a


  • Recognise and use expressions in decimal form
• MS 1c


  • Use ratios, fractions and percentages
• MS 1d


  • Make estimates of the results of simple calculations
• MS 4a


  • Translate information between graphical and numeric form
• MS 4b


  • Drawing and interpreting appropriate graphs from data to determine rate of reaction
• MS 4c


  • Plot two variables from experimental or other data
• MS 4d


  • Determine the slope and intercept of a linear graph
• MS 4e


  • Draw and use the slope of a tangent to a curve as a measure of rate of change
• Factors which affect the rates of chemical reactions

  • Concentrations of reactants in solution
  • Pressure of reacting gases
  • Surface area of solid reactants
  • Temperature
  • Presence of catalysts
• Students should be able to recall how changing these factors affects the rate of chemical reactions
• This topic offers opportunities for practical work and investigations in addition to required practical 5
• Required practical 5: investigate how changes in concentration affect the rates of reactions by a method involving measuring the volume of a gas produced and a method involving a change in colour or turbidity
• This should be an investigation involving developing a hypothesis
• AT skills covered by this practical activity

  • 1
  • 3
  • 5
  • 6
• This practical activity also provides opportunities to develop WS and MS
• Collision theory


  Explains how various factors affect rates of reactions. According to this theory, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy
• Activation energy


  The minimum amount of energy that particles must have to react
• Increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants


  Increases the frequency of collisions and so increases the rate of reaction
• Increasing the temperature


  Increases the frequency of collisions and makes the collisions more energetic, and so increases the rate of reaction
• Students should be able to predict and explain using collision theory the effects of changing conditions of concentration, pressure and temperature on the rate of a reaction
• Students should be able to predict and explain the effects of changes in the size of pieces of a reacting solid in terms of surface area to volume ratio
• Students should be able to use simple ideas about proportionality when using collision theory to explain the effect of a factor on the rate of a reaction
• Catalysts


  Change the rate of chemical reactions but are not used up during the reaction. Different reactions need different catalysts. Enzymes act as catalysts in biological systems

  
• Catalysts increase the rate of reaction by

  Providing a different pathway for the reaction that has a lower activation energy

  
• Students should be able to identify catalysts in reactions from their effect on the rate of reaction and because they are not included in the chemical equation for the reaction
• Students should be able to explain catalytic action in terms of activation energy
• Students do not need to know the names of catalysts other than those specified in the subject content
• An opportunity to investigate the catalytic effect of adding different metal salts to a reaction such as the decomposition of hydrogen peroxide

  
• Reversible reactions


  In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called reversible reactions and are represented: A + B ⇌ C + D