1. Collision theory

2. Starter – how fast does a reaction go?
Some reactions are very slow
Some proceed much more quickly
For example…

3. Speed of reaction

6. Demonstration Reactions can be so fast that you don’t get burned…

7. Rate of reaction
How fast a reaction proceeds is just another way of describing the reaction “rate”
Why would we want to control the rate of reaction?
Because we want to make more products in less time using less energy
What are the five factors that can affect rate of reaction?
Can you guess? If not, look at the next slide for answers:

8. Collision theory
In order to react, reactant particles must collide with each other
When they collide they must be in the correct orientation AND must have sufficient energy.
If we can make more collisions happen then the rate of reaction will increase (forming more products)
How can we do this?

9. Factors which affect rate
Temperature (increasing it would increase the speed at which the reactant molecules collide and so more products will form)
Concentration (by adding more reactant molecules, more collisions will take place and so more products will form)
Pressure (increasing it would make the container smaller, which will increase collisions and so more products will form)
Surface area (making the reactant molecules smaller will increase the possibility of collisions and so more products will form)
Catalysts (adding a catalyst -usually in powder form, to increase its surface area- will lower the energy barrier for the reaction and increase the rate, and so more products will form) `

10. Speeding up reactions
Anything that increases the chance of effective collision increases the rate (speed) of reaction. Factors include:
Increased surface Area
Increased concentration
Increased temperature
Use of a catalyst
Increased pressure

11. Past paper question

12. Mark scheme