A pH indicator is used to determine the acidity of a substance. It changes color based on the pH level of the solution, allowing for easy identification of whether a solution is acidic, neutral, or basic. Thus, the correct answer is option A, acidity. ;
A pH indicator is used to determine the acidity of a substance by changing color based on the pH level of the solution. The correct answer to the question is option A, acidity. Other properties listed cannot be measured using a pH indicator.
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