The pH scale measures how acidic or basic (alkaline) a solution is by quantifying the concentration or activity of hydrogen ions (H⁺) in that solution. It is a logarithmic scale ranging from 0 to 14:
- A pH less than 7 indicates an acidic solution, meaning it has a higher concentration of hydrogen ions.
- A pH of exactly 7 is neutral, indicating equal concentrations of hydrogen ions and hydroxide ions (OH⁻), as in pure water.
- A pH greater than 7 indicates a basic or alkaline solution, meaning it has a lower concentration of hydrogen ions and a higher concentration of hydroxide ions
Because the scale is logarithmic, each one-unit change in pH represents a tenfold change in acidity or basicity. For example, a solution with pH 4 is ten times more acidic than one with pH 5
. In summary, the pH scale measures the acidity or alkalinity of aqueous solutions by indicating the relative concentration of hydrogen ions present. This measurement is important in chemistry, biology, environmental science, and many other fields
