Acidic substances dissolve in water to give an acidic solution.
Basic substances dissolve in water to give a basic (or alkaline) solution.
A solution can be classified as either acidic or basic by observing the colour of pH-sensitive dyes (indicator).
This can be done by either
Litmus paper has been impregnated with a mixture of dyes that are extracted from lichens.
Basic substances dissolve in water to give a basic (or alkaline) solution.
A solution can be classified as either acidic or basic by observing the colour of pH-sensitive dyes (indicator).
This can be done by either
adding a small portion of the dye to the solution.
OR more conveniently by dipping strips of paper impregnated with the dye(s) into the solution.
OR more conveniently by dipping strips of paper impregnated with the dye(s) into the solution.
Litmus paper has been impregnated with a mixture of dyes that are extracted from lichens.
Blue litmus paper to test for acidity.
Pink litmus paper to test for basicity.
Pink litmus paper to test for basicity.
 | ||||
| pH | ||||
| litmus dry litmus wet | ||||
| change | blue to red | neither | red to blue | |
The diagram shows strips of red and blue litmus before and after it is dipped into a solution. If the solution is
neutral, both red and blue litmus are unchanged (except for wetting).
basic (pH higher than 7), red litmus turns blue.
acidic (pH lower than 7), blue litmus turns red.
basic (pH higher than 7), red litmus turns blue.
acidic (pH lower than 7), blue litmus turns red.