Specification Point 3.12:
Know that a catalyst is a substance that increases the rate of a reaction, but is chemically unchanged at the end of the reaction

Catalyst

Catalyst: A substance that increases the rate of a reaction, but is chemically unchanged at the end of the reaction.

  • Catalyst will be chemically unchanged so mass will stay the same.

Energy level diagram:

Energy level diagram, Edexcel IGCSE Chemistry

How a catalyst increases the rate of a reaction

Specification Point 3.13:
Know that a catalyst works by providing an alternative pathway with lower activation energy

Catalyst: A substance that increases the rate of a reaction, but is chemically unchanged at the end of the reaction

  • The catalyst will provide an alternative pathway requiring lower activation energy so more colliding particles will have the necessary activation energy to react
  • This will allow more frequent and successful collisions per second, increasing the rate of reaction

Energy Level Diagrams

*Activation energy without catalyst:

Activation energy without catalyst, Edexce lIGCSE Chemistry

*Activation energy with catalyst:

Effect of using a catalyst, CIE IGCSE Chemistry

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.