Rates of Reaction

• Rate of a chemical reaction

  How fast the reactants are changed into products
• Slow reactions

  • Rusting of iron
  • Chemical weathering (like acid rain damage to limestone)
• Moderate speed reaction

  • Metal magnesium reacting with an acid to produce a gentle stream of bubbles
• Fast reactions

  • Burning
  • Explosions
• Collision theory

  The rate of a chemical reaction depends on the collision frequency of reacting particles and the energy transferred during a collision
• Factors affecting reaction rates

  1. Collision frequency

  2. Energy transferred during a collision
• Successful collision

  A collision in the particles reacting to form products
• Activation energy

  The minimum amount of energy that particles need to react
• Particles need activation energy to break the bonds in the reactants and start the reaction
• The steeper the line on the graph, the faster the rate of reaction
• The quickest reactions have the steepest lines and become flat in the least time
• Graphs 1, 2, and 3 all converge at the same level, showing that they all produce the same amount of product although they take different times to produce it
• Graph 4 shows more product and a faster reaction, which can only happen if more reactant(s) are added at the start