What is the characteristic of a substance characterized as an amphoteric?

A substance characterized as amphoteric can react with both acids and bases, which is the defining trait of amphoterism. This means it has the ability to either donate a proton (acting as an acid) or accept a proton (acting as a base) depending on the nature of the reactants it is interacting with.

For example, water (H₂O) is a classic amphoteric substance because it can react with hydrochloric acid (HCl) to act as a base, forming hydronium ions (H₃O⁺), and with sodium hydroxide (NaOH) to act as an acid, producing hydroxide ions (OH⁻). This dual capability allows amphoteric substances to play versatile roles in chemical reactions, often helping to maintain pH balance in various systems.

When considering the other options, acting only as an acid or only as a base excludes the capacity to act in both ways, which directly contradicts the amphoteric definition. Additionally, while the production of hydrogen ions in solution is a characteristic of acids, it does not encompass the full behavior of amphoteric substances, as these can also behave as bases by accepting protons. Thus, the correct answer emphasizes the unique quality of amphoteric substances to engage