Water is amphoteric, which means it can behave as either an acid or a base, depending on the context in which it is placed. In pure form, water is neutral, with a pH of 7. However, when it dissolves other substances, it can become acidic or basic. When water reacts with an acid, it donates a pair of electrons to the acid, forming hydronium ions (H3O+) and conjugate bases. When water reacts with a base, it accepts a pair of electrons from the base, forming hydroxide ions (OH-) and conjugate acids.