Discuss key concept of evolution theory of Darwin.

Explanation

The number of collision that takes place per second per unit volume of the reaction mixture is known as Collision frequency. The collisions which actually produce the products and therefore, result in chemical reaction are called effective collision.
There are two important barriers to a reaction namely:
(1) Energy barrier (2) Orientation barrier.
(1) Energy barrier : For reacting species to make effective collisions, they should have sufficient energy to break the chemical bonds in reaction molecule. The minimum amount of energy which the colliding molecule must possess is known as threshold energy.
(2) Orientation barrier : The colliding molecule should also have proper orientation so that the old bonds may break and new bond formed example:
`NO_(2(g)) + NO_2 to N_2O_4(g)`
During the reaction, the product are formed only when colliding molecule have proper orientation at time.

(a) Properly oriented collision form product