Explain in terms of particles and collisions how concentration, temperature and addition of a catalyst affect the rate of a reaction.

Concentration: the higher the concentration, the more particles in the same volume. The increase in particle numbers causes an increase in particle collisions, so the rate of reaction increases.Temperature: at higher temperatures the rate of reaction increases. This is because the particles have more energy, so move around faster. This increases the chance of particle collisions so increases the rate of reaction.Addition of a catalyst: catalysts provide a different route for the reaction which has a lower activation energy. This means that more of the particle collisions will be effective so the rate of reaction increases.