The pH scale tells you how acidic or alkaline a solution is. It runs from 0 to 14, and the pH of a solution can be measured with a pH probe or with universal indicator. A neutral solution has a pH of 7. Pure water is neutral.
Acidic solutions have a pH lower than 7, and the lower the number, the more acidic the solution. Alkaline solutions have a pH higher than 7, and the higher the number, the more alkaline the solution.
For example, hydrochloric acid might have a pH of 1, so it is acidic. Sodium hydroxide solution might have a pH of 13, so it is alkaline. A solution with a pH of 7 is neither acidic nor alkaline.
