What term is used to describe reactions that break compounds down into simpler substances?

The term that describes reactions breaking compounds down into simpler substances is decomposition reactions. During a decomposition reaction, a single compound undergoes a process that results in the formation of two or more products. This process may involve various types of energy input, such as heat, light, or electricity, to dissociate the chemical bonds within the compound.

For example, when water (H2O) is decomposed into hydrogen and oxygen gases through electrolysis, it illustrates a clear case of a decomposition reaction. Such reactions are fundamental in chemistry as they illustrate how more complex substances can be separated into their constituent components.

The other types of reactions mentioned serve different purposes: substitution reactions involve the replacement of one part of a compound with another; addition reactions entail the combination of two or more reactants to form a larger, more complex product; while combination reactions specifically refer to the formation of one compound from multiple reactants. Understanding these distinctions is essential for grasping fundamental chemical principles.