.4 catalysts

• Catalysts change the rate of chemical reactions but are not used up during the reaction. Different reactions need different catalysts. Enzymes act as catalysts in biological systems.
• Catalysts increase the rate of reaction by providing a different pathway for the reaction that has a lower activation energy
• reaction profile for a catalysed reaction:

  
• A catalyst lowers the activation energy so more particles have sufficient energy to reach the top of the hill and start the reaction. Therefore, there is a higher frequency of successful collisions between reactant particles and hence a greater number of products formed per unit time.