Final answer:
The logarithmic nature of the pH scale means that a one unit change in pH corresponds to a ten-fold change in hydrogen ion concentration, representing the relative acidity or alkalinity of solutions.
Step-by-step explanation:
The logarithmic nature of the pH scale means that a change of one pH represents a ten-fold change in ion concentration. This can be understood by the formula pH = -log [H+], where [H+] is the concentration of hydrogen ions. A pH value of 1 indicates a [H+] that is ten times greater than that of a pH value of 2. Importantly, the pH of a substance can indicate its acidity or alkalinity; a pH lower than 7 is acidic, higher than 7 is alkaline, and a pH of 7 is neutral, which is the pH of pure water.
For example, a solution with a pH of 4 has a hydrogen ion concentration that is ten times that of a solution with a pH of 5. The relative acidity or alkalinity of a solution becomes more intuitive when studying the pH scale. The scale consolidating a wide range of acidity into numbers that are more easily comparable exemplifies the convenient use of a logarithmic scale in chemistry.