pH

pH is a measure of how acidic or basic (alkaline) a solution is. It is a scale that ranges from 0 to 14:

• pH less than 7: The solution is acidic. The lower the pH, the more acidic the solution is.
• pH of 7: The solution is neutral, meaning it is neither acidic nor basic. Pure water is an example of a neutral solution.
• pH greater than 7: The solution is basic (alkaline). The higher the pH, the more basic the solution is.

The pH scale is logarithmic, meaning each whole number change on the scale represents a tenfold change in the concentration of hydrogen ions.
For example, a solution with a pH of 4 is ten times more acidic than a solution with a pH of 5.

In chemical terms, pH is defined as the negative logarithm (base 10) of the hydrogen ion concentration [H⁺] in a solution:

pH = −log[𝐻⁺]

This means that as the concentration of hydrogen ions increases, the pH value decreases, indicating higher acidity.