Rates of reaction

• hypothesis: If... (the change), then... (what happens)
• Independent = change
• Dependent = what you measure
• Controlled = what stays the same
• Rate of reaction is a measure of how fast or slow a chemical reaction happens (fast = explosion, slow = rusting)
• The collision theory states that for a chemical reaction to occur, the particles must collide with enough energy, and the particles need to collide in the right way (both need to occur).
• Factors affecting rate of reaction

  • temperature
  • surface area
  • concentration
  • catalysts
• Temp increase = particles move faster because they have more kinetic energy (Ek), which increases the frequency of successful collisions. This then increases the rate of reaction.
• Temp decrease = particles move slower because they have less kinetic energy (Ek), which decreases the frequency of successful collisions. This then decreases the rate of reaction.
• Concentration increase (number of particles in a given volume) = increased number of particles which increases the frequency of successful collisions. This increases the rate of reaction.
• Concentration decreases (the number of particles in a given volume) = decreased number of particles, which decreases the frequency of successful collisions. This decreases the rate of reaction.
• Surface area increases = more surfaces of particles are exposed, which increases the frequency of successful collisions. This increases the rate of reaction.
• Surface area decreases = less surfaces of particles are exposed, which decreases the frequency of successful collisions. This decreases the rate of reaction.
• Catalysts (a substance added to a chemical reaction)

  • does not react with reactants in a chemical reaction
  • a substance that increases the rate of reaction
  • reduces the amount of energy needed for a successful collision.