Rate and extent of chemical change

• What does collision theory say?

  • the more collisions that faster the reaction

  • particles must react with enough energy - activation energy
• What things effect rate of reaction?

  • temperature

  • concentration or pressure

  • surface area

  • presence of a catalyst
• How does increasing the temperature increase the reaction rate?

  • particles more faster

  • collide more frequently

  • more of the collisions will have enough energy
• How does increasing the concentration or pressure increase the reaction rate?

  • concentration - more particles in same volume

  • pressure - same amount of particles in smaller volume

  • makes collisions more frequent
• How does increasing the surface area increase the reaction rate?

  • increases the surface area to volume ratio

  • same volume of of solid - more area to work on

  • collisions are more often
• How does using a catalyst increase the reaction rate?

  lowers the activation energy so particles do not require as much energy for collisions to be successful
• How do you work out the rate of a reaction?

  amount of reactants used or amount of product formed ÷ time
• What affects the position of equilibrum?

  • temperature

  • pressure

  • concentration
• What is Le Chatelier's principle?

  if you change conditions of reversible reaction at equilibrium the system will try to counteract change
• What is endothermic?

  energy transferred from surroundings (heats up)
• What is exothermic?


  energy transferred to surroundings (cools down)
• How does temeprature affect equilibrium?

  • decreasing temp favours exothermic direction (making more products on that side)

  • increasing temp favours endothermic direction (making more products on that side)
• How does pressure affect equilibrium?

  • increasing pressure the equilibrium tries to reduce it - moves direction with less molecules

  • decreasing pressure the equilibrium tries to increase it - moves direction with more molecules
• How does concentration affect equilibrium?


  • increasing reactants the equilibrium tries to decrease it - makes more products

  • decreasing products the equilibrium tries to increase it - makes less reactants