How do you increase the rate of a reaction?

A reaction will occur if two reactants collide with each other with enough energy to overcome the 'activation energy'. The activation energy is the minimum amount of energy the reactant particles need in order to react. Therefore to increase the rate of a reaction, more reactant particles need to collide with an energy greater than the activation energy.

There are 4 ways to increase the rate of a reaction:

Increasing the Temperature

When you increase the temperature, the reactant particles have more heat energy. This is converted into kinetic energy so the particles move faster. This has 2 consequences; the number of collisions increases and these collisions occur at a higher energy so are more likely to result in a reaction. Therefore more reactant particles collide at an energy which is above the activation energy, hence the rate of reaction increases.

Increasing the Concentration / Pressure

As concentration increases, reactant molecules are closer together (there are more molecules in a given space). This means more collisions occur so more successful collisions take place. Therefore the reaction rate increases.

Increasing the Surface Area (in Solids)

An example of increasing surface area would be grinding up limestone pebbles to a powder. This increases the rate of reaction because more reactant particles are exposed to each other (i.e. the particles in the middle of the limestone pebble would be exposed to the reactant if the pebble were ground to powder) so there is a greater chance of collisions. With more collisions comes a greater reaction rate.

Adding a Catalyst

A catalyst is a substance which increases the rate of reaction without being used up or changed in the process. The catalyst speeds up the rate of reaction as it provides a lower activation energy, so the reactant particles can collide with less energy but still result in a reaction. It's important, however, to remember that a catalyst only works for a specific reaction.