What factors affect rate of reaction?

In order for a reaction to occur, particles must 1. COLLIDE with each other 2. with sufficient KINETIC ENERGY (energy greater than or equal to the ACTIVATION ENERGY). This is known as Collision Theory. There are different factors that can change rate of reaction by affecting either the frequency of collisions or the energy the particles have.

1. TEMPERATURE: Increased temperature means increased heat energy. This is transferred to kinetic energy. There are more collisions per unit time with sufficient energy so the rate increases.

2. SURFACE AREA: increased surface area (i.e. a powder instead of a lump of the substance) means that there are more particles in contact with each other. There are more sucessful collisions per unit time so the rate increases.

3. CONCENTRATION OF REACTANTS: Higher concentrations mean more particles in the same volume. There are more collisions occuring so more successful collisions per unit time and the rate increases.

4. CATALYST: Catalysts don't affect the frequency of successful collisions directly but work in another way. They lower the activation energy by providing an alternative pathway. This means more particles will have energy greater than or equal to the activation energy so there are more successful collisions per unit time and the rate is increased. REMEMBER: catylsts are not used up in the reaction themselves and don't affect the reaction in any other way than the rate.