GCSE Combined Science (AQA)

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Surface Area & Rate

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The rate and extent of chemical change Rate of reaction

Surface Area & Rate

6:45 Factors Affecting Rate of Reaction
Spec 4.6.1.2 4.6.1.3
Previous Collision Theory & Reaction Rate Next Reaction Profile for Catalysed Reaction
  • Many reactions involve solid reactants, such as the reaction between solid metal carbonate (e.g., calcium carbonate) and aqueous acid.
  • Increasing the surface area of solid reactants increases the rate of reaction.
  • Reaction rate graphs can compare reactions using solids with different surface areas.
  • A solid with a smaller surface area results in a lower rate of reaction, indicated by a shallow curve on the graph.
  • A solid with a larger surface area results in a higher rate of reaction, indicated by a steeper curve on the graph.
  • Surface area is the area over which reactant particles can collide and react.
  • Collision theory states that reactants must collide with sufficient energy for a reaction to occur.
  • Smaller pieces of solid reactant have a greater surface area to volume ratio than larger pieces.
  • Splitting a solid into smaller pieces increases the surface area while keeping the volume the same.
  • Increasing the surface area increases the frequency of collisions between reactant particles and the solid.
  • The rate of reaction increases as the surface area to volume ratio increases.
  • Using smaller lumps of solid reactant produces a faster rate of reaction than larger lumps.
  • Powdered reactants have the fastest rate of reaction due to their high surface area to volume ratio.
  • Commercial reactants, like biological washing powders, are often manufactured in powdered form to facilitate faster reactions.

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