Key concepts:

• Catalysts are substances that bring reacting molecules together.
• Reacting molecules are held close to one another on the surface of the catalyst.
• Interactions between the catalyst and the reacting molecules lower the activation energy barrier, and the chemical reaction takes place.
• The product molecules are released from the surface of the catalyst and the process can begin again.
• Many inorganic catalysts are metals, with lots of surface area where the reacting molecules can be brought together.