TOPIC 1 - C6 Rates - AQA combined chem paper 2

• the rate of a chemical reaction is how fast the reactants are changed into products
• one of the slowest rate of chemical reaction is the rusting of iron and chemical weathering
• chemical weathering like acid rain can bring damage to limestone buildings
• a moderate speed reaction would be metal magnesium reacting with acid to produce a gentle stream of bubbles
• burning is a fast reaction however explosions re faster and release aloyt more gas
• reactions rates are explained by collison theory
• the rate of reaction depends on collision theory and energy transferred during a Collision
• Collision frequency


  How often reacting particles collide
• More collisions


  Faster the reaction
• Energy transfer during a collision


  Particles have to collide with enough energy for collision to be successful
• Activation energy

  The minimum amount of energy that the particles need to react
• Particles need activation energy to break the bonds in the reactants and start the reaction
• Factors that increase the rate of reaction

  • Increased proportion of reacting particles colliding
  • Increased amount of energy particles collide with
• Factors that affect the rate of reaction

  • Temperature
  • Surface area
  • Presence of a catalyst
  • Concentration of a solution or presence of a gas
• More collisions increase the rate of reaction
• All four methods of increasing the rate of reaction can be explained in terms of increasing the number of successful collisions between the reacting particles
• Increasing the temperature

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

  Particles move faster, so they collide more frequently, and the faster they move the more of the collisions will have enough energy to make reactions happen
• Increasing the concentration or pressure

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

  More particles in the same volume or space, so collisions between reactants are more frequent
• Increasing the surface area

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

  More area for the same volume of solid reactant, so more collisions between particles
• Using a catalyst


  Increases the rate of reaction
• How a catalyst increases the rate


  It provides an alternate reaction pathway with a lower activation energy, so reactions can occur more easily
• Catalysts are not used up in the reaction
• increasing temperature increases the kinetic energy of the particles which means there will be more successful collisions
• collisions between particles must have enough kinetic energy to overcome activation energy
• if there's not enough energy, then no reaction will occur
• activation energy is the minimum amount of energy required for a successful collision