What does the pH scale measure?

The pH scale is a numeric scale used to specify the acidity or basicity of an aqueous solution. It measures the concentration of hydrogen ions (H⁺) present in the solution. A lower pH value indicates a higher concentration of hydrogen ions, reflecting a more acidic solution, while a higher pH value indicates a lower concentration of hydrogen ions, signifying a basic or alkaline solution.

This measurement is crucial in many fields, including chemistry, biology, and environmental science, as it can affect chemical reactions, biological processes, and the behavior of substances in water.

The other options do not accurately describe what the pH scale measures. The temperature of a solution is unrelated to its pH and is measured using a thermometer. The mass of chemical components involves different measurements, often using scales to quantify substances. Similarly, the density of solutions pertains to the mass per unit volume of a substance and is measured through other means, not through the pH scale.