A decomposition reaction is one in which:

1. The name describes what happens to the reactant: it comes apart. 2. One reactant breaks down into two or more products. 3. Two reactants joining to form a single product is the reverse case, a combination reaction. 4. An element replacing another in a compound is displacement, as when zinc displaces hydrogen from acid. 5. Two solutions producing an insoluble solid is precipitation, identified by the solid that appears. _Source: NECTA CSEE 2021 Chemistry 032, Question 1: Multiple Choice, item (vi)_