What is the pH Scale? The pH scale is a numerical scale ranging from 0 to 14 that measures how acidic or basic (alkaline) a substance is. The term "pH" stands for "potential of hydrogen," which refers to the concentration of hydrogen ions (H⁺) in a solution. Acidic substances have a pH between 0 and 6.9. Neutra l substances have a pH of 7 (e.g., pure water). Basic (alkaline ) substances have a pH between 7.1 and 14. The pH scale is logarithmic, meaning each unit represents a tenfold difference in acidity or alkalinity. For example, a substance with a pH of 3 is 10 times more acidic than a pH of 4 and 100 times more acidic than a pH of 5. Why is the pH Scale Important? 1. pH in Everyday Life The pH scale plays a crucial role in daily activities, from the food we eat to the products we use. For instance: Lemon juice (pH 2-3) is highly acidic. Coffee (pH 5) is mildly acidic. Milk (pH 6.5-6.7) is slightly acidic. Soap (pH 9-10) is alkaline. 2. pH in the Human B...