6.2.2. & 6.2.3. I can define activation energy and describe collision theory using three factors which affect the rate of reaction

Definition of activation energy	Minimum value of kinetic energy which particles must have before they're able to react.
Three factors that affect the rate of reaction	1. Collision frequency
	2. Number of particles with a greater kinetic energy than the activation energy
	3. Collision geometry or orientation

6.2.2.   Define the term activation energy

Activation energy is defined as the minimum value of kinetic energy which particles must have before they're able to react.

6.2.3.    Describe the collision theory

The rate of reaction will depend on the frequency of collisions which occur between particles possessing both:

• Values of kinetic energy greater than the activation energy
• Appropriate collision geometry

When reactants are laced together, the kinetic energy that the particles possess causes them to collide with each other. The energy of these collisions results in some bonds between the reactants being broken and new bonds being formed. 

The rate of the reaction will depend on the number of collisions between particles which are successful - which lead to the formation of products. Not all collisions will be successful and there are two reasons for this: energy of collision and geometry of collision. 

1. Energy Of Collision

The particles must have a certain minimum value for their kinetic energy in order for a collision to lead to a reaction. This energy is necessary to overcome repulsion between molecules and to break some bonds in the reactants before they can react. 

When this energy is supplied, the reactants achieve the transitions state from which products can form. The energy required represents an energy barrier for the reaction and is known as the activation energy.

The value of activation energy varies greatly from one reaction to another and the magnitude of this value plays an important part in determining the overall rate of reaction. The rate of the reaction depends on the proportion of particles that have values of kinetic energy greater than the activation energy.

2. Geometry Of Collision

Because collisions between particles are random, they're likely to occur with the particles in many different orientations. This can be crucial in determining whether or not the collisions will be successful and therefore what proportion of collisions will lead to a reaction.