You have been provided with three test-tubes. One of these test -tubes contain distilled water and the other two contain an acidic and a basic solution respectively. If you are given only blue litmus paper, how will you identify the contents of each test-tube?

The following steps should be followed in order to identify the contents of the test-tube.

Step 1: The test tube containing distilled water will not bring any change in the colour of blue litmus paper.

Step 2: Blue litmus paper turns red when dipped in acidic solution.

Step 3: Initially, the third test tube will have no change on the blue litmus paper. But, when the red litmus paper from step 2 is used, it changes the colour back to blue. Hence, indicating that it is a base.