Here's why:

* The pH scale: The pH scale measures the acidity or alkalinity of a solution. It ranges from 0 to 14.

* Acids: Acids have a high concentration of hydrogen ions (H+).

* pH and H+ concentration: The lower the pH, the higher the concentration of H+ ions, and the more acidic the solution.

Therefore, a very acidic solution would have a pH close to 0.

For example:

* pH 1: Very strongly acidic

* pH 3: Strongly acidic

* pH 7: Neutral (like pure water)

* pH 11: Strongly alkaline (basic)