What does pH indicate about a solution?

pH is a measure of the hydrogen ion concentration in a solution, which directly indicates the acidity or alkalinity of that solution. A pH value lower than 7 signifies an acidic environment, while a pH value higher than 7 indicates alkalinity. A pH of 7 is considered neutral, meaning the solution is neither acidic nor alkaline. Understanding pH is crucial in many applications, especially in water quality monitoring, as it affects chemical reactions, biological activity, and overall water quality.

In this context, the other options do not accurately represent what pH measures. The presence of bacteria in water is typically assessed through microbial testing rather than pH. The level of dissolved solids pertains to the concentration of minerals and salts present in the water, which is measured separately from pH. Finally, temperature is a distinct physical parameter that is not related to pH and is measured using thermometers or temperature probes rather than with pH indicators.