What term describes the ability of water to resist changes in pH?

The term that describes the ability of water to resist changes in pH is buffering capacity. This concept is crucial in water treatment and environmental science because it relates to how well water can maintain a stable pH level despite the addition of acidic or alkaline substances. Buffers are solutions that can absorb excess hydrogen ions (H+) or hydroxide ions (OH-) without significantly changing the pH of the solution. This characteristic is vital for aquatic life and many chemical processes, ensuring that the water remains within a favorable pH range for biological functions.

Alkalinity, while related to buffering capacity, specifically refers to the measurement of the capacity of water to neutralize acids. It is one of the components that contribute to the overall buffering capacity but does not encompass the full concept of how water can resist pH fluctuations.

Osmotic pressure describes the pressure required to prevent the flow of water across a semipermeable membrane due to a solute concentration gradient, which does not relate to pH stability. Volatility typically refers to how easily a substance can evaporate or turn into vapor, which also does not apply in this context. Thus, buffering capacity accurately captures the ability to maintain pH stability in water.