Collision Theory and Reaction Rate PowerPoint

Year 11 Collision Theory, reaction rate, activation energy and orientation

1. Collision Theory
Miss Chendeb

2. Chemical Reactions
Chemical reactions vary widely in the speeds with which they occur.
➢ Some reactions occur very quickly. If a lighted match is brought in
contact with lighter fluid or another flammable liquid, it erupts into flame
instantly and burns fast.
➢ Other reactions occur very slowly. A container of milk in the
refrigerator will be good to drink for weeks before it begins to turn sour.
➢ Millions of years are required for dead plants under Earth’s surface to
accumulate and eventually turn into fossil fuels such as coal and oil.

3. What is Collision Theory?
-Collision theory explains how chemical reactions occur and why
reaction rates differ.
-It focuses on the collision between reacting particles as the driving
force behind reactions.
-Proposed by Max Trautz & William Lewis

4. Key Concepts
-Reactant particles must collide with enough energy to overcome the
activation energy barrier.
-Collisions must occur with proper orientation for the reaction to
proceed.
-Not all collisions result in a reaction; only those with enough
activation energy and correct orientation are successful.

5. What is Activation Energy
The activation energy for a
reaction is the minimum energy
that colliding particles must have
in order to undergo a reaction.

6. A low activation energy means that a lot of the particles will collide with
enough energy to react. The reaction will be fast.
A high activation energy means that far fewer particles will collide with
enough energy. The reaction will be slow.

7. So what’s correct orientation?
Orientation: the relative position or direction of something.
Example: CO + NO2 -> CO2 + NO

8. Another Example!

9. And another one :)

10. Reaction Rate
The reaction rate can be
determined by measuring how fast
the concentration of A or B
decreases, or by how fast the
concentration of AB increases.
-Red line - reactants
-Blue line - products

11. Factors Affecting Reaction Rate
By their nature, some reactions occur very quickly, while others are very
slow. However, certain changes in the reaction conditions can have an
effect on the rate of a chemical reaction. Collision theory can be utilised to
explain these rate effects. Those factors are:
-Temperature
-Surface Area
-Concentration of reactants
-Pressure
-Catalyst