The pH scale is a numerical scale ranging from 0 to 14 that measures how acidic or basic (alkaline) a solution is. It is based on the concentration of hydrogen ions (H⁺) in a solution.
- A pH of 7 is neutral, like pure water.
- A pH less than 7 indicates an acidic solution (more H⁺ ions).
- A pH greater than 7 indicates a basic or alkaline solution (fewer H⁺ ions or more OH⁻ ions).
The scale is logarithmic, meaning each whole number change represents a tenfold difference in acidity or alkalinity. For example, a solution with pH 4 is 10 times more acidic than one with pH 5.
The pH scale is vital in chemistry, biology, agriculture, medicine, and environmental science, as many chemical reactions and biological processes are highly sensitive to pH levels.