Reaction Rates
Chapter 12.1 and 12.4 of
A Natural Approach to Chemistry
Rates of Reactions
 How fast does a reaction occur?
Why Do We Care?
Sometimes we
need to slow
reactions
down.
Sometimes we need
reactions to happen
quickly.
Why Do We Care?
How do we know if a reaction is going to
occur quickly or slowly?
Better yet, how can we
control the rate of a
reaction?
Rate of Reaction
Rate of Reaction - how fast a reaction occurs
decrease
-how quickly the amount of reactants __________
increase
-how quickly the amount of products __________
Collision Theory
Collision Theory – In order to react, reactant
molecules must collide with each other
How does this relate to reaction rates?
In order to increase reaction rate, we must increase
the number of collisions.
Factors Affecting Reaction Rate
1) Temperature – hotter temperatures
faster
mean: ____________
molecules
increase
molecular collisions ___________
Reaction rate __________
increases
Factors Affecting Reaction Rate
Which of these will have more collisions?
Low Concentration
High Concentration
Factors Affecting Reaction Rate
2) Concentration – higher concentration
means:
more reactant molecules
_______
molecular collisions ___________
increase
Reaction rate __________
increases
Factors Affecting Reaction Rate
Which of these will have more collisions?
Low Surface Area
High Surface Area
Factors Affecting Reaction Rate
3) Surface Area – higher surface area
means:
more reactant molecules available
_______
for collisions
molecular collisions ___________
increase
increases
Reaction rate __________
Factors Affecting Reaction Rate
Factors Affecting Reaction Rate
increases
4) Catalyst – molecule that ____________
the reaction rate without getting used up
in the reaction itself
How does it do this?
- It lowers the activation energy of the
reaction