Which of the following describes a substance with a pH level below 7?

A substance with a pH level below 7 is classified as acidic. The pH scale ranges from 0 to 14, where a pH of 7 is considered neutral, indicating that the solution is neither acidic nor basic. Values below 7 denote increasing acidity, with lower numbers corresponding to stronger acids. For example, lemon juice and vinegar are common acidic substances with pH levels well below 7.

The other classifications pertain to pH levels in different ranges. A neutral substance has a pH of exactly 7, while basic or alkaline substances are those that have a pH above 7, indicating they are less acidic and have a higher concentration of hydroxide ions compared to hydrogen ions. Therefore, identifying a substance with a pH below 7 as acidic aligns with the definitions in chemistry regarding the nature of pH and the behavior of substances.