1. Rates of Reaction
Aim: To revise the 4 factors that affect rates
Aim: To revise methods of measuring rates

2. Rates of Reaction
Reactions occur because there are successful collisions between reactant particles, i.e. they collide in the correct direction and with enough energy to overcome the minimum amount of energy needed to start a reaction, the activation energy Ea.
Anything that increases the frequency of these collisions will increase the rate.

3. Rates of Reaction
The rate is a measure of how fast the products are made or reactants are used up

4. Rate = change in reaction
Rates of Reaction
Rate = change in reaction
time
e.g. Change in volume gas made
If the amount of product made is constant then the change in the reaction is a constant and is given the value 1, so rate = 1

5. Rates of Reaction
An example of this type of reaction is the “disappearing cross” where a constant amount of precipitate is made

6. Rates of Reaction Concentration
Doubling the concentration will double the number of particles and hence double the chance of successful collisions, therefore the reaction should take half the time and the rate should be twice as fast

7. Rates of Reaction Surface area
The more particles that are exposed, the higher the frequency of successful collisions therefore faster the rate

8. Rates of Reaction Temperature
This gives particles more energy so they collide with more energy and more frequently. More of the particles have energy ≥ EA . This increases rate as there are more successful collisions

9. Rates of Reaction Catalyst
This provides a surface for the reaction to take place on and hence increases the frequency of collisions. It also provides a different route for the reaction with a lower activation energy. This means that more of the collisions will result in a reaction

10. Rates of Reaction
This could be measured using the loss in mass of a gas, e.g.

11. Rates of Reaction
This could be measured by collecting a volume of gas, e.g.