Here's why:

* pH Scale: The pH scale measures the acidity or alkalinity of a solution. It ranges from 0 to 14, with 7 being neutral.

* Pure Water: Distilled water is essentially pure H₂O. When pure water dissociates, it forms equal amounts of hydrogen ions (H+) and hydroxide ions (OH-). This balanced ratio results in a pH of 7.

* Impurities: However, distilled water can become slightly acidic or alkaline if it absorbs impurities from the air or container it's stored in.

In summary, distilled water is typically neutral (pH 7) but can become slightly acidic or alkaline due to environmental factors.