What does pH measure?

pH measures the concentration of positive hydrogen ions (H⁺) in a solution. This is crucial because the pH scale ranges from 0 to 14, where lower values indicate higher concentrations of hydrogen ions (making the solution more acidic), and higher values indicate lower concentrations (making the solution more alkaline). Specifically, a pH of 7 is considered neutral, such as that of pure water.

Understanding pH in terms of hydrogen ion concentration allows scientists and chemists to determine how acidic or basic a substance is. It provides vital information about the chemical environment, which is essential in various applications, including biology, environmental science, and industrial processes.

The other options do not accurately reflect what pH measures. The strength of an acid is related but not the same as pH; it pertains to how completely an acid dissociates in solution. Temperature changes can affect pH but are not what pH measures. Volume is a separate property entirely, unrelated to the acid-base characteristics described by pH.