Changes

pH equal to 7 is considered to be neutral.  This is the pH of pure water at a temperature of 25 °C.

pH equal to 7 is considered to be neutral.  This is the pH of pure water at a temperature of 25 °C.

pH is a logarithmic scale based on the concentration of protons(H+) in the solution. Thus, a change of  pH by 1 corresponds to a change in concentration by a factor of 10.  In general, the pH of most substances varies from 0 to 14 although for some extreme cases the pH can be greater than 14 or less than 0.

pH is a logarithmic scale. Roughly, it can be considered to be based on the concentration of protons(H+) in the solution.<ref>Actually, it is based on something called the hydrogen ion ''activity.'' Activity is approximately the same as concentration for dilute solutions in nearly pure water.</ref>  Thus, a change of  pH by 1 corresponds to a change in concentration by a factor of 10.  In general, the pH of most substances varies from 0 to 14 although for some extreme cases the pH can be greater than 14 or less than 0.