Catalysts
A A substance that changes the rate of a chemical reaction without being changed by the reaction itself. is a substance that:
- increases the rate of a reaction
- does not alter the A substance formed in a chemical reaction. of the reaction
- is not chemically changed or used up at the end of the reaction
Only a very small mass of catalyst is needed to increase the rate of a reaction. However, not all reactions have suitable catalysts. Different substances catalyse different reactions.
Catalysts in biological reactions are called A protein which catalyses or speeds up a chemical reaction.. Catalysts do not appear in the overall chemical equation for a reaction.
How catalysts work
A catalyst provides an alternative The sequence of reactions needed to produce a desired product from a particular set of raw materials. that has a lower The minimum amount of energy that colliding particles must have for them to react. than the uncatalysed reaction. This does not change the frequency of collisions. However, it does increase the frequency of successful collisions because more particles have energy greater than the activation energy, therefore there are more successful collisions.
The effect of a catalyst on the activation energy is shown on a chart called a Chart showing how the energy of reactants and products changes during a reaction.. This shows how the The capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow. of the A substance that reacts together with another substance to form products during a chemical reaction. and products change during a reaction.