Final answer:
The pH of shampoo is typically slightly acidic with a pH less than 7, to maintain healthy hair and avoid irritation.
Step-by-step explanation:
The pH of shampoo for maintaining healthy hair is typically slightly acidic, with a pH less than 7. This slight acidity helps with keeping the hair and scalp clean, providing minimal skin and eye irritation, and helping to repair damage to the hair. On the pH scale, which ranges from 0 to 14, substances with a pH below 7 are considered acidic, while those with a pH above 7 are considered basic (alkaline). The pH scale itself is a negative logarithmic scale where a change by one pH unit represents a ten-fold change in hydrogen ion concentration ([H+]). Therefore, the pH of shampoo is designed to be close to the pH of natural hair, avoiding extremes in pH which can be damaging.