Litmus paper is the most recognized member of chemical indicators. Like most pH paper, litmus changes color when exposed to an acidic or basic solution. The simple pH scale ranges from 0-14 with 0 being the most acidic, 7 being neutral, and 14 being the most basic or alkaline. Litmus paper is commonly used in educational science classes. Because it has such wide recognition, it has become a cultural reference in our society as well. It is common to use the term litmus test when referring to a test in which a single factor determines the outcome.