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Home > Chemistry > Revision videos > Rates of reactions


Rates of reactions

Rates of reactions

The speed of a chemical reaction is affected by four factors: concentration, temperature, particle size, and the presence of a suitable catalyst. This video shows demonstrations that illustrate each of these factors.

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Key learning points:

  • Particles must collide for a chemical reaction to happen.
  • The rate of a reaction depends on the frequency and energy of collisions between particles.
  • Starch reacts with iodine to turn blue/black
  • Increasing concentration increases reaction rate because the collisions are more frequent.
  • Increasing temperature speeds up a reaction because there are more collisions and the collisions have higher energy.
  • Catalysts speed up reactions by increasing the number of successful collisions.
  • Catalysts are not used up in a reaction.
  • Smaller particles have a larger surface area.
  • Increasing surface area increases a rate of reaction.


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