Collision theory states that chemical reactions occur when reactant particles collide with sufficient energy to overcome the activation energy barrier. For a collision to result in a reaction, the particles must collide with proper orientation. The rate of reaction increases with factors that increase the frequency and success of collisions, such as higher concentrations or temperatures of reactants, presence of a catalyst, increased surface area, agitation, and reactants with weaker bonds. A catalyst lowers the activation energy required for reaction, allowing more collisions to have sufficient energy.
2. Collision theory is a theory that was proposed independently by Max Trautz in
1916 and William Lewis in 1918.
The collision theory states that when suitable particles of the reactant hit each
other, only a certain fraction of the collisions cause any noticeable or significant
chemical change; these successful changes are called successful collisions.
The successful collisions must have enough energy, also known as activation
energy, at the moment of impact to break the pre-existing bonds and form all
new bonds. This results in the products of the reaction.
Collision theory
3. Increasing the concentration of the reactant particles or raising the
temperature - which brings about more collisions and hence more
successful collisions - therefore increases the rate of a reaction.
When a catalyst is involved in the collision between the
reactant molecules, less energy is required for the chemical
change to take place, and hence more collisions have
sufficient energy for reaction to occur. The reaction rate
therefore increases.
4. Factors that affect KINETICS
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one another
with enough energy (activation energy) and must collide in the right orientation.
FACTORS:
1) Concentration of reactants
2) Temperature
3) Presence of a catalyst
4) Surface area
5) Agitation
6) Nature of reactants
5. Factor 1: Concentration
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one
another with enough energy (activation energy) and must collide in the right orientation.
FACTORS:
1) Concentration of reactants
If you increase concentration (Molarity), the rate of reaction increases.
Why? There are more molecules which increases the number of collisions
altogether; however, there are better chances that molecules will collide in
the right orientation.
6. Factor 2: Temperature
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one another with
enough energy (activation energy) and must collide in the right orientation.
FACTORS:
2) Temperature
Temperature is an averaged kinetic energy of molecules so if you increase
temperature, you increase kinetic energy. This means you increase the number of
collisions
Heat supplies the energy to allow the reaction to proceed (i.e. overcoming the
activation energy barrier)
Think about: Why do we refrigerate milk?
7. Factor 3: Presence of Catalyst
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one another with enough energy
(activation energy) and must collide in the right orientation.
FACTORS:
3) Presence of a catalyst
Catalyst assist a reaction and increase the reaction rate without being consumed in the reaction.
Adding a catalyst decreases the activation energy which means more molecules will have
enough energy to react.
Think about: Catalytic converter, Enzymes
9. Factor 4: Surface Area
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one another with
enough energy (activation energy) and must collide in the right orientation.
FACTORS:
4) Surface Area
Increased surface areas of molecules/particles will increase the rate of reaction. This
means to break into smaller particle sizes.
More places to react give better chances for collisions in the right orientation.
How to increase surface area? Grind or crush a mixture of reactants.
Ex: A crushed aspirin will enter your blood stream faster than taking it whole.
10. Factor 5: Agitation
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one
another with enough energy (activation energy) and must collide in the right orientation.
FACTORS:
5) Agitation
Stirring or shaking a reaction will increase the reaction rate.
By stirring or shaking, you are introducing energy into the reaction and
thus giving molecules/particles more energy to react (overcome activation
energy barrier). Your mechanical energy is converted to kinetic energy.
11. Factor 6: Nature of Reactants
All based on COLLISION THEORY:
Collision theory: For a reaction to occur, the atoms or molecules must collide with one another
with enough energy (activation energy) and must collide in the right orientation.
FACTORS:
6) Nature of reactants
Reactants whose bonds are weaker have a lower activation energy and thus a
higher rate of reaction.
All chemical reactions involve bond breaking and bond making. Bond breaking
occurs on reactant side. Collisions between reactants that require less kinetic
energy are needed to break weaker bonds (i.e. smaller activation energy)
