Which of the following is true about the pH scale?

The pH scale is a logarithmic scale, meaning that each whole number change on the scale represents a tenfold change in acidity or alkalinity. For example, a solution with a pH of 3 is ten times more acidic than a solution with a pH of 4. This logarithmic nature makes it an important tool for measuring the concentration of hydrogen ions in a solution, which directly affects its acidity. It is particularly relevant in hair coloring, where the pH can influence the opening of the hair cuticle and, consequently, the absorption of color.

On the scale, 0 to 7 indicates acidity, 7 is neutral, and 7 to 14 indicates alkalinity. While some may think the scale extends from 1 to 15, it traditionally ranges from 0 to 14 in most contexts, so the idea that it has a broader range is not accurate. Additionally, the pH scale measures both acidic and alkaline properties rather than solely focusing on acidity, and it does not directly determine hair color, although it does affect the hair dyeing process.