Surface Area : Volume-

• For a given mass of a solid, large lumps have smaller surface area to volume ratios than smaller lumps or powders
• If a large lump is divided or ground into a powder:

  • Its total volume stays the same
  • The area of exposed surface increases
  • The surface area to volume ratio increases
• The greater the frequency of successful collisions, the greater the rate of reaction
• If the surface area to volume ratio of a reacting solid is increased:

  • More reactant particles are exposed at the surface
  • The frequency of collisions between reactant particles increases
  • Therefore, the rate of reaction increases
• Note that the mean energy of the particles does not change. However, since the frequency of collisions increases (they happen more often) the frequency of successful collisions also increases