C2(ii) - Rates of Reaction 5.

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Many reactions can be speeded up by adding a catalyst.

A catalyst is a substance which changes the speed of a reaction, without being changed or used up in the reaction.

1) Catalysts Lower the Activation Energy.

a) The activation energy is the minimum amount of energy needed for a reaction to happen.

b) It's a bit like having to climb up one side of a hill before you can fall down the other side.

c) Catalysts lower the activation energy of the reaction, making it easier for it to happen.

d) This means a lower temperature can be used.

2) Solid Catalysts Work Best When They Have a Big Surface Area.

a) Catalysts are usually used as a powder or pellets or a fine gauze.

b) This gives them a very large surface area to enable the reacting particles to stick to giving more chance for a collision.

c) Transition Metals are common catalysts in many industrial reactions, e.g. nickel is used for…


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