When litmus paper is added to HCl, a strong acid, it will turn red. This is because HCl donates H+ ions to the solution, which causes the pH to decrease and the litmus paper to change color.
When litmus paper is added to methyl benzene, a nonpolar organic compound, it will not change color. This is because methyl benzene does not donate or accept H+ ions, so the pH of the solution does not change.
