A pH indicator is a ___________ chemical molecule that is introduced to a solution in small doses to allow the pH (acidity or basicity) to be visually assessed.
A teacher of Class VIII demonstrates the following activity in her class "The teacher takes a small amount of sulphur in a spoon and burns it. She then puts the spoon into a tumbler with a lid to ensure that the gas produced does not escape. After a few minutes, she adds water to the tumbler." What happens if blue and red litmus papers are put into the tumbler?
