Factors Affecting Rates of Reaction

• Factors that affect the rate of reaction


  • Temperature
  • Concentration of a solution (or pressure of a gas)
  • Surface area of a solid
  • Whether a catalyst is used
• Increasing the temperature


  Increases the rate of reaction
• How increasing temperature increases the rate of reaction


  1. Particles move faster

  2. Particles collide more frequently (often)

  3. Particles have more energy, so more collisions have enough energy to make the reaction
• Increasing the concentration or pressure

  Increases the rate of reaction
• How increasing concentration or pressure increases the rate of reaction


  1. If a solution is more concentrated, it has more particles in the same volume

  2. When the pressure of a gas is increased, the same number of particles are now in a smaller space

  3. Collisions between the reactant particles are more frequent
• Increasing the surface area

  Increases the rate of reaction
• How increasing surface area increases the rate of reaction


  1. If one of the reactants is a solid, breaking it up into smaller pieces will increase its surface area to volume ratio

  2. This means the same amount of solid has a bigger surface

  3. More of the solid's particles are available to particles of other reactant, and collisions will be more frequent
• Catalyst


  A substance that speeds up a reaction without being consumed or permanently altered
• How a catalyst increases the rate of reaction


  1. Catalysts work by providing a different pathway for a reaction

  2. The new pathway has a lower activation energy, so less energy is needed for the reaction to happen
• Enzymes


  Biological catalysts that catalyse reactions in living things
• Catalysts are not part of the reaction equation
• Different catalysts are needed for different reactions