C2: Rates of Reaction

The rate of a chemical reaction increases:

• if the temperature increases
• if the concentration of dissolved reactants or the pressure of gases increases
• if solid reactants are in smaller pieces (greater surface area)
• if a catalyst is used

chemical reactions only happen when reacting particles collide with sufficient energy (activation energy).

activation energy = the minimum amount of energy particles must have to react

Increasing the temperature:

Increases the speed of the reacting particles (move faster)

The particles collide more frequently and with more energy

There are more successful collisions

This increases the rate of reaction

Concentrations of solutions is measured in moles per cubic decimetre (mol/dm³)

Increasing the concentration of reactants in solution and increasing the pressure in reacting gases:

Makes the particles crowd together

The particles will collide more often

Resulting in more successful collisions

Increases the rate of reaction

Large particles have a small surface area in relation to their volume

To increase the surface area you can make the particles smaller by using powder or simply cutting them

By increasing the surface area:

There will be more chances for the particles to collide resulting in more successful collisions

Increasing the rate of reaction

Catalyst = a substance which increases the rate of a chemical reaction without being used up or altered in the process

All catalysts are reusable

Catalysts are important as they reduce costs of an experiment

By using catalysts:

The amount of energy needed for successful collisions is lowered

So there are more successful collisions

Increasing the rate of reaction

To figure out the rate of reaction you do:

The amount of reactant used/product formed (divided by) The time taken for reaction to finish