What is the pH level of pure water?

Pure water has a neutral pH level of 7 at 25 degrees Celsius (77 degrees Fahrenheit), which is considered the standard temperature for pH measurement. This neutrality means that it is neither acidic nor basic. The pH scale itself ranges from 0 to 14, where values below 7 indicate acidity and values above 7 indicate alkalinity.

In the context of the other options, a pH of 5.5 indicates a weakly acidic solution, which would not qualify as pure water. A pH of 9.5 and 10 suggest a basic solution, which again moves away from the characteristics of pure water. Understanding the pH of substances is vital in fields such as chemistry, biology, and cosmetology, especially when formulating products that need to maintain certain pH levels for stability and safety.