Here's why:

* Neutral pH: A pH of 7 is considered neutral.

* Autoionization of water: Water molecules can self-ionize, meaning they can donate or accept protons (H+). This creates a small concentration of H+ ions and OH- ions.

* Equal concentrations: In pure water, the concentration of H+ ions is equal to the concentration of OH- ions. This balance leads to a neutral pH of 7.

It's important to note that the pH of water can change based on temperature and the presence of impurities.