What is indicated by a color change in a pH indicator?

A color change in a pH indicator signifies a change in acidity or alkalinity, which is a fundamental property of the solution being tested. pH indicators are organic compounds that exhibit different colors at different pH levels due to their chemical structure altering in response to the concentration of hydrogen ions (H⁺) in the solution.

When the pH of the solution changes—either becoming more acidic (lower pH) or more alkaline (higher pH)—the indicator undergoes a chemical transformation that leads to the observable color change. This property makes pH indicators useful tools for visualizing the pH level of a solution, thus providing immediate qualitative information about its acidity or alkalinity.

In contrast, factors such as temperature, concentration, or osmotic pressure do not directly affect the pH indicator itself in terms of color change. Thus, while they can influence the properties of the solution being measured, they do not represent the specific function of pH indicators in signaling changes in acidity or alkalinity.