What does the pH scale measure?

The pH scale specifically measures the concentration of hydrogen ions (H+) in a solution. It is a logarithmic scale that reflects how acidic or basic a solution is based on the activity of these ions. A lower pH value indicates a higher concentration of hydrogen ions, which signifies an acidic solution, while a higher pH value indicates a lower concentration of hydrogen ions, signifying a basic (or alkaline) solution.

Although the presence of hydroxide ions (OH-) is related, as their concentration inversely correlates with hydrogen ion concentration in aqueous solutions, the primary focus of pH measurement is on the concentration of hydrogen ions. Other factors, such as the temperature and the density of a solution, do not directly relate to how pH is quantified or understood in the context of acidity and basicity. The pH scale is a fundamental concept in both chemistry and biology, providing insight into the chemical environment of a solution, which can affect reactions, biological processes, and overall solution behavior.