Collision Theory

Collision theory

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This accounts for the factors that influence the rate of reaction.

For a reaction to occur the reacting particles must collide with each other.

A collision only results in the formation of products if a certain minimum energy is exceeded in the collision - this is then described as an effective collision.

An effective collision: occurs when bonds are broken and new bonds are formed, bringing about the formation of products.



The rate of reaction depends on the number of e effective collisions per second between reacting particles.

Activation Energy: 

is the minimum energy that colliding particles must have for a reaction to occur. Denoted Ea.

Low activation energy means a faster rate. Conversely, high activation energy means a slower rate.

1. Temperature:
increased temperature means that the kinetic energy of the molecules increases. Therefore, more collisions occur and hence more effective collisions must occur.

2. Nature of the reactants:
covalent compounds have to break bonds to react and
therefore they need more energy and so they have a higher activation energy.

3. Particle size:
smaller particles have a larger surface area for more collisions to occur. Therefore, more e ective collisions will occur and hence they will reach the activation energy more rapidly.

4. Concentration:
greater concentration means more particles and therefore more collisions, and hence more e ective collisions. Thus, the activation energy is reached more rapidly.

5. Catalyst:
it provides an alternative pathway with a lower activation energy.


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