Particle Size

• Decreasing the particle size increases the rate of reaction
• Decreasing particle size increases surface area; more reactant particles exposed to collide so the successful collision rate increases. This results in an increased rate of reaction

  
• Explosive combustion

  • Fine particles are combustible in air due to larger surface area
  • The rate of reaction is high making them explosive
  • Examples: methane gas in coal mines and flour milling