What is the pH scale and how does it work?

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is neutral (pure water), below 7 is acidic, and above 7 is basic. It is a logarithmic scale, so each unit change represents a tenfold change in hydrogen ion concentration. For example, pH 4 is ten times more acidic than pH 5. Indicators like litmus, phenolphthalein, and universal indicator are used to determine pH. pH is important in biological systems, agriculture, and industrial processes.