Water molecules break into hydrogen and oxygen gas when electrical energy is applied through electrolysis.
While the anode creates oxygen gas, the cathode produces hydrogen gas, which is visible as bubbles and is accompanied by a hissing sound. The evolved hydrogen gas, which is extremely flammable and emits a pop sound when ignited, can be used to test flammability. In general, the process of electrolysis of water shows how to divide water into its component gases by use of an electric current.