Decomposition reactions are chemical processes where a single compound breaks down into two or more simpler substances. This type of reaction often occurs when energy, such as heat, light, or electricity, is applied to the compound. For example, when water is subjected to electrolysis, it decomposes into hydrogen and oxygen gases. These reactions are important in various fields, including chemistry and environmental science. They can be classified into different types, such as thermal decomposition, where heat is used, and photodecomposition, which involves light. Understanding decomposition reactions helps in studying chemical reactions and their applications in real-world scenarios.