Here's why:

* The pH scale ranges from 0 to 14.

* 0 is the most acidic, and 14 is the most alkaline (basic).

* 7 is neutral (like pure water).

* Anything above 7 is alkaline (basic).

A pH of 11 is very high on the scale, indicating a strong base. Substances with this pH might include:

* Strong household cleaners

* Some types of drain cleaners

* Lye (sodium hydroxide)

It's important to remember that strong alkalis can be dangerous. They can cause skin and eye irritation, and in higher concentrations, they can be corrosive.