Decomposition is a type of chemical reaction in which one or more compounds are broken down into simpler compounds or elements. This is the opposite of a synthesis reaction, in which two or more elements or simple compounds combine to create one or more slightly more complex compounds.
The airbag of a car uses a decomposition chemical reaction to make the bag expand. When the car senses an accident, a small device sends an electrical current to sodium azide pellets contained in the airbag. The electricity causes the pellets to rapidly decompose into nitrogen gas and sodium, filling the airbag with air.