Decomposition brought about by heat is known as thermal decomposition. What is the difference between thermal dissociation and thermal decomposition?
Thermal decomposition is the process of decay enacted upon a molecule due to naturally occurring environmental conditions. Thermal dissociation is the breaking apart of a molecule's bonds due to the introduction of heat.
Thermal dissociation is a simple, single-step reaction where a molecule splits into two products. Usually, only one bond breaks and the reaction is reversible. Examples of thermal dissociation are:
CH3Br → CH3 + Br
CH3CH3 → CH3 + CH3
Thermal decomposition implies a multi-step reaction with a complicated mixture of products. The process is not reversible. An example of thermal decomposition is the formation of crud on the bottom of the pan when something is overcooked on the stove, or in the bottom of the flask when a reaction is overheated.