Decomposition

Decomposition is a reaction where a complex substance reacts and breaks down into simpler parts. Or a compound is broken up in to two or more substances. A simple represntation can be seen below:

AB --> A + B

Here AB is the compund that is broken up. A and B are the products after the reaction takes place. In this reaction, AB yields the substances A and B.

The process of breaking down water into hydrogen gas and oxygen gas is a decomposition reaction. The equation is shown below:

Reactant -----> Product + Product

Basically combination and decomposition reactions are reverse reactions of each other..