collision theory

Click a letter for the index

Or search the encyclopaedia:

 

 

Go

 

Click image to enlarge
Theory that explains how chemical reactions take place and why rates of reaction alter. For a reaction to occur the reactant particles must collide. Only a certain fraction of the total collisions cause chemical change; these are called successful collisions. The successful collisions have sufficient energy (activation energy) at the moment of impact to break the existing bonds and form new bonds, resulting in the products of the reaction. Increasing the concentration of the reactants and raising the temperature bring about more collisions and therefore more successful collisions, increasing the rate of reaction.

When a catalyst undergoes collision with 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.

Red recalls the banner of Manas who united the Kyrgyz tribes. The emblem shows a bird's-eye view of a yurt, secured by a lattice of ropes. Effective date: 3 March 1992. >>