What is the range of the pH scale?

The pH scale is a measurement of how acidic or basic a substance is, and it ranges from 0 to 14. This scale provides a way to quantify the concentration of hydrogen ions in a solution, with lower numbers indicating higher acidity and higher numbers indicating higher alkalinity. A pH of 7 is considered neutral, meaning that the concentration of hydrogen ions and hydroxide ions are equal.

Understanding this scale is crucial in cosmetology, as many products used in hair and skin care are formulated within this range to ensure safety and effectiveness. For example, shampoos and conditioners may have a pH range close to that of the natural pH of hair, which is typically between 4.5 and 5.5. Using products outside of the recommended pH range can lead to issues such as dryness or irritation, emphasizing the importance of knowing the full span of the pH scale.

The other options provided do not reflect the complete and standard range of the pH scale, which is why they are not correct. The pH scale does not extend to 10, 15, or limit itself to 7, as these numbers do not encompass the full range of acids and bases commonly encountered in various substances.