What does pH measure in a solution?

pH is a scale used to specify how acidic or alkaline a solution is, which directly relates to the concentration of hydrogen ions (H⁺) present in that solution. A lower pH value indicates higher acidity, meaning more hydrogen ions are present, while a higher pH value signifies a more alkaline (basic) solution, indicating fewer hydrogen ions.

This scale typically ranges from 0 to 14, with 7 being neutral. For instance, substances like vinegar have a pH less than 7, which categorizes them as acidic, while substances like baking soda have a pH greater than 7, indicating they are alkaline. The ability to measure and interpret pH is crucial in various scientific fields, including chemistry, biology, and environmental science, as it affects many chemical reactions and biological processes in nature.

The other options provided do not relate to the measurement of pH; temperature relates to thermal energy, pressure relates to the force exerted by molecules in a substance, and density measures mass per unit volume. None of these concepts address the specific characteristics of acidity or alkalinity, which is the core focus of pH measurement.