P - Kinetics 1
Collision Theory:
Chemical reactions occur when reactant particles collide with energy greater
than or equal to the activation energy to break the bonds. The collision must also
take place between the parts of the molecules that are going to react together,
so orientation is important.
Most collisions between molecules do not result in reactions because they either
do not have enough energy or they are in the wrong orientation.
Factors affecting rate of reaction:
Temperature: Increasing temperature increases the average KE of the particles.
This results in the particles to move faster and collide with more energy. Hence,
frequency of collisions and frequency of successful collisions increases as more
particles would have the activation energy. So rate of reaction increases.
Concentration: Increasing concentration increases the number of particles per
unit volume, hence the frequency of collisions between reactant particles
increases, so frequency of successful collisions increases. So rate of reaction
increases. However, as a reaction proceeds, the concentration of reactant
particles decreases as they are used up, rate of reaction drops as reactions
goes on.
Pressure: Increasing pressure results in more particles per unit volume, resulting
in frequency of collisions and successful collisions to increase. So rate of
reaction increases.
Surface area: The more the total SA of the solid, the more of its particles are
available to collide with molecules in a liquid or gas. Hence, frequency of
collisions and successful collisions increaes. So rate of reaction increases. This
means that breaking a lump into smaller pieces increases rate of reaction as
there are more sites for reaction.
Catalyst: Rate of reaction increases when a catalyst is used as the catalyst
provides an alternate reaction pathway that has a lower activation energy, so
more particles have the activation energy, so frequency of successful collisions
P - Kinetics 1 1
Collision Theory:
Chemical reactions occur when reactant particles collide with energy greater
than or equal to the activation energy to break the bonds. The collision must also
take place between the parts of the molecules that are going to react together,
so orientation is important.
Most collisions between molecules do not result in reactions because they either
do not have enough energy or they are in the wrong orientation.
Factors affecting rate of reaction:
Temperature: Increasing temperature increases the average KE of the particles.
This results in the particles to move faster and collide with more energy. Hence,
frequency of collisions and frequency of successful collisions increases as more
particles would have the activation energy. So rate of reaction increases.
Concentration: Increasing concentration increases the number of particles per
unit volume, hence the frequency of collisions between reactant particles
increases, so frequency of successful collisions increases. So rate of reaction
increases. However, as a reaction proceeds, the concentration of reactant
particles decreases as they are used up, rate of reaction drops as reactions
goes on.
Pressure: Increasing pressure results in more particles per unit volume, resulting
in frequency of collisions and successful collisions to increase. So rate of
reaction increases.
Surface area: The more the total SA of the solid, the more of its particles are
available to collide with molecules in a liquid or gas. Hence, frequency of
collisions and successful collisions increaes. So rate of reaction increases. This
means that breaking a lump into smaller pieces increases rate of reaction as
there are more sites for reaction.
Catalyst: Rate of reaction increases when a catalyst is used as the catalyst
provides an alternate reaction pathway that has a lower activation energy, so
more particles have the activation energy, so frequency of successful collisions
P - Kinetics 1 1
