Substances cannot be both acidic and alkaline at the same time. The pH scale is a measure of the acidity or alkalinity of a substance, and it ranges from 0 to 14. A pH of 7 is considered neutral, while a pH below 7 is acidic and a pH above 7 is alkaline. It is not possible for a substance to have a pH below 7 and above 7 at the same time.