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Topic 6:Chemical Kinetics

6.1 Collision Theory and Rates of Reaction
Essential Idea:
  • The greater the probability that molecules will collide with sufficient energy and proper orientation, the higher the rate of reaction.
  • Species react as a result of collisions of sufficient energy and proper orientation.
  • The rate of reaction is expressed as the change in concentration of a particular reactant/product per unit time.
  • Concentration changes in a reaction can be followed indirectly by monitoring changes in mass, volume and colour.
  • Activation energy (Ea) is the minimum energy that colliding molecules need in order to have successful collisions leading to a reaction.
  • By decreasing Ea, a catalyst increases the rate of a chemical reaction, without itself being permanently chemically changed.
Applications & Skills:
  • Description of the kinetic theory in terms of the movement of particles whose average kinetic energy is proportional to temperature in Kelvin.
  • Analysis of graphical and numerical data from rate experiments.
  • Explanation of the effects of temperature, pressure/concentration and particle size on rate of reaction.
  • Construction of Maxwell–Boltzmann energy distribution curves to account for the probability of successful collisions and factors affecting these, including the effect of a catalyst.
  • Investigation of rates of reaction experimentally and evaluation of the results.
  • Sketching and explanation of energy profiles with and without catalysts.
Nature of Science:
  • The principle of Occam’s razor is used as a guide to developing a theory—although we cannot directly see reactions taking place at the molecular level, we can theorize based on the current atomic models. Collision theory is a good example of this principle.
PPT: Collision Thoery & Reaction Rates
Collision Theory Animations
BBC: Rates of Reaction
Khan Academy: Collision Theory & Activation Energy
How to speed up chemical reactions (and get a date)
Video: Activation Energy
Analyzing Rate Graphs
How to speed up chemical reactions (and get a date)
Thornley: Maxwell Boltzmann Review
Maxwell Boltzmann Simulation
pHet Reactin Rate Simulation
Reaction Rate Simulation