Amphoteric Substance
A substance able to react as either an acid or a base depending on what it meets.
Unit
Dimensionless
In depth
Amphoterism is characteristic of the oxides and hydroxides of metals near the metal–non-metal boundary, which dissolve in both acid and alkali. It also describes amino acids, which bear both an acidic carboxyl group and a basic amino group in the same molecule.
Examples in the real world
Al(OH)₃ dissolving in HCl to give Al³⁺ and in NaOH to give the aluminate ion; ZnO behaving the same way.