What reaction shows a compound breaking apart into separate subtances?

A reaction that shows a compound breaking apart into separate substances is called a decomposition reaction. In this type of reaction, a single compound is broken down into two or more simpler products, often due to the application of heat, light, or electricity. An example is the thermal decomposition of calcium carbonate (CaCO₃), which breaks down into calcium oxide (CaO) and carbon dioxide (CO₂) when heated.