C3 - C

  • Created by: zoolouise
  • Created on: 02-06-15 17:23
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  • Rate of reaction (3)
    • Explosions and surface area
      • Combustible powders can cause explosions.
        • Some powders react with oxygen to make volumes of carbon dioxide and water vapor.
          • The owners of a factory using combustible powders such as flour, custard powder or sulfur must be very careful. They must ensure that the powders can't reach the open atmosphere and that the chances of a spark being produced near the powders is small.
      • Breaking up a block into smaller pieces increases the surface area.
      • A powdered reactant has a larger surface area than the same mass of reactant in block form.
        • As the surface area of a solid is increased, so is the rate of reaction.
      • In a small surface area, the solid block particles are trapped at the bottom and most particles in the solid block cant react as collisions only occur on the surface.
        • Powders can spread throughout a reaction mixture, increasing the collision frequencies.
          • In a solid block, collisions can only occur on on the surface, however, most of the particles are trapped on the inside and therefore they arent available to react.
      • In a large surface area the solid particles from the block are spread out and there are more surfaces on the particles exposed, so more collisions are possible and this increases rate of reaction.
        • Reactions occur when reactant particles collide with sufficient energy.
    • Catalysts and rate of reaction
      • A catalyst changes the rate of reaction and remains unchanged at the end of the reaction.
      • Only a small quantity of catalyst is needed to catalyses a large mass of reactants.


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