What is an amphoteric substance?

An amphoteric substance is characterized by its ability to act as either an acid or a base, depending on the surrounding conditions or the substances it interacts with. This dual functionality is crucial in many chemical reactions and biological processes. For example, water is a classic amphoteric substance; it can donate a proton (H⁺) in an acidic environment, acting as an acid, or accept a proton in a basic environment, acting as a base.

In the context of the provided options, the choice stating that an amphoteric substance can be either an acid or a base, depending on the environment, accurately captures this behavior. This property is particularly important for buffering systems in biological systems, where maintaining pH balance is vital.

The other options misrepresent the concept of amphotericity. An option stating that a substance can only act as an acid or only as a base does not reflect the fundamental definition of an amphoteric substance, which inherently includes both actions. Similarly, stating a substance neutralizes only strong acids does not convey its context-dependent nature, as amphoteric substances respond differently based on their chemical environment rather than being limited to interactions with strong acids alone.