Decomposition in chemistry refers to a chemical reaction in which a single reactant breaks down into two or more products. This process is also known as chemical breakdown and is usually regarded as the opposite of chemical synthesis. Decomposition reactions can be generally classified into three categories: thermal, electrolytic, and photolytic decomposition reactions. Some common examples of decomposition reactions include the electrolysis of water to yield hydrogen and oxygen, and the decomposition of carbonic acid in soft drinks. Decomposition reactions are used for several analytical techniques, notably mass spectrometry, traditional gravimetric analysis, and thermogravimetric analysis. Additionally, decomposition reactions are used today for a number of other reasons in the production of a wide variety of products, such as the explosive breakdown reaction of sodium azide into nitrogen gas and sodium.