Defining an Amphoteric Substance
An amphoteric substance is a molecule or ion that has the ability to react as either an acid or a base. This dual reactivity depends entirely on the substance it is reacting with. The term originates from the Greek word 'amphoteros,' meaning 'both'.
Section 2: How It Works
The behavior of an amphoteric substance is determined by its chemical environment. When it is in the presence of a strong acid, it will behave as a base by accepting protons (H⁺). Conversely, when it is in the presence of a strong base, it will behave as an acid by donating protons.
Section 3: A Practical Example: Water
Water (H₂O) is the most common example of an amphoteric substance. When reacting with an acid like hydrochloric acid (HCl), water acts as a base: HCl + H₂O → H₃O⁺ + Cl⁻. When reacting with a base like ammonia (NH₃), water acts as an acid: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻.
Section 4: Importance of Amphoteric Substances
Amphoteric substances are vital in many chemical and biological systems. For instance, amino acids, the building blocks of proteins, are amphoteric, which allows them to act as buffers in the body to maintain pH balance. They are also important in analytical chemistry and industrial processes for controlling acidity.