10.1 Reaction rates

• Rate of a chemical reaction is the change in concentration of a product or reactants over time
• Collision theory states that for a reaction to take place, the colliding particles must have enough energy to react
• Activation energy is the minimum amount of energy needed for a reaction to take place
• The lower the activation energy, the larger the number of particles that can react
• Changing concentration affects the rate of reaction for reactions that involve solutions and gases
• Increasing concentration

  • reactant particles are closer together
  • more frequent collisions
  • rate increases
• Increasing pressure only affects gaseous molecules, not solid or liquid molecules
• To find the rate at any point on a graph:

  • draw tangent at the point
  • calculate gradient of tangent
• As the reaction proceeds, the reactants are used up, concentration decreases and the rate of reaction decreases