Which substance is known for maintaining a consistent pH level in water?

A buffer is a substance that helps to maintain a stable pH level in a solution, such as water. It achieves this by neutralizing acids or bases that are added, preventing significant changes in pH. This is crucial in many chemical and biological processes, where a stable pH is essential for proper function. Buffers typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid.

In contrast, a neutralizer refers more broadly to a substance that neutralizes acids or bases, but it does not necessarily maintain pH balance over time like buffers do. An acid and an alkaline solution both inherently change pH levels; an acid lowers pH, while an alkaline solution raises it. Therefore, while these substances affect pH, they do not stabilize it, underscoring the unique role of a buffer in maintaining pH consistency.