Yes, a substance can be a Brønsted–Lowry acid but not an Arrhenius acid. An example is ammonia gas (NH₃). When it reacts with hydrogen chloride gas (HCl), it forms ammonium chloride. In this reaction, ammonia accepts a proton from HCl, making it a base according to Brønsted–Lowry. However, neither NH₃ nor HCl produced H+ or OH- ions in water in this reaction, so by the Arrhenius definition, neither can be classified as an acid or base. This example illustrates the broader applicability of the Brønsted–Lowry theory compared to the Arrhenius theory.

The Arrhenius theory, as previously mentioned, defines acids as substances that produce hydrogen ions in aqueous solutions and bases as substances that produce hydroxide ions. While this theory is accurate, it's restrictive in scope, only applicable to reactions in aqueous solutions. The Brønsted–Lowry theory, by focusing on proton donation and acceptance, is a more inclusive definition. It encompasses the reactions described by the Arrhenius theory (as they involve proton transfers) but also includes other proton transfer reactions outside aqueous environments. Thus, the Brønsted–Lowry theory can be seen as a broader generalisation of the Arrhenius concept.

Amphoteric substances can act as both acids and bases. This directly ties in with the Brønsted–Lowry theory, which defines acids as proton donors and bases as proton acceptors. An amphoteric substance has the flexibility to either donate or accept a proton depending on the reaction conditions and the substances it reacts with. Water, as discussed earlier, is a classic example of an amphoteric substance. The concept of amphoterism, while not exclusive to the Brønsted–Lowry theory, fits comfortably within its framework, further showcasing the theory's ability to explain a wide range of acid-base behaviours.

Water is unique in its ability to act as both an acid and a base, a property termed "amphoteric". According to the Brønsted–Lowry theory, an acid donates a proton and a base accepts a proton. In the reaction between water and ammonia, for example, water donates a proton to ammonia, acting as an acid. Conversely, when water reacts with hydrogen chloride, it accepts a proton from HCl, behaving as a base. This dual nature arises due to the molecular structure of water, allowing it to either lose a proton or gain a proton, depending on the reaction conditions.

The Brønsted–Lowry theory focuses on the transfer of protons (H+ ions) in acid-base reactions. In this theory, an acid is a proton donor and a base is a proton acceptor. The Lewis acid-base theory, on the other hand, revolves around the transfer of electron pairs. A Lewis acid is an electron-pair acceptor, while a Lewis base is an electron-pair donor. Therefore, while the Brønsted–Lowry theory restricts its definition to proton transactions, the Lewis theory is more general, encompassing a broader range of reactions through its focus on electron pairs.