You are given three test tubes. The three test tubes contain distilled water, acidic solution and the basic solution respectively. There is only red litmus paper available in order to identify what is there in each test tube. How will you find out what is in each of the test tubes?

Red litmus paper can be used to identify the content in each test tube. Variation in color of Red Litmus Paper can help in identifying the content.
Red litmus paper has characteristic that it turns blue when is treated with base and turns purple when is treated with a neutral solution. Change of color of the red litmus paper can be observed in the following ways:
(i) If the red litmus paper changes to blue colour the solution is a basic solution.

(ii) If the red litmus paper experiences no change the solution is an acidic solution.

(iii) If the red litmus paper changes to purple colour the solution is distilled water.