What does pH measure in a solution?

pH specifically measures the acidity or basicity of a solution by determining the concentration of hydrogen ions (H⁺) present. Creating a pH scale, which typically ranges from 0 to 14, allows us to classify substances as acidic, neutral, or basic. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic solution. A pH of 7 is considered neutral, such as pure water.

The pH is a logarithmic scale, meaning that each whole number change represents a tenfold increase or decrease in hydrogen ion concentration. Thus, pH is a critical parameter for understanding chemical properties, biological processes, and environmental conditions. By focusing on the relationship between hydrogen ions and solution properties, pH provides important insights into chemical reactivity, metabolic processes, and ecological balances.

In contrast, other options address different aspects of a solution. Temperature relates to thermal energy, not the concentration of ions or acidity. The concentration of ions, while relevant, does not encapsulate the specific measurement that pH represents—it is rather a broader term. Solubility pertains to how well a solute dissolves in a solvent, which is unrelated to the concept of pH.