Class 7 Chemistry Acids, Bases and Salts Indicators


Substances that are used to indicate whether a substance is acid or a base are known as indicators. They change their colour on addition of a solution containing an acidic or a basic substance. In our day to day life we get to see many examples where indicators change their colour when comes in contact with acid or base. For instance, while washing clothes if a shirt having a spot of curry turns to reddish brown when comes in contact with the detergent soap but soon disappears when washed thoroughly. This is due to the presence of base in detergent that changes the colour of the turmeric indicator.

 There are several types of indicators used in our day to day life. Some of them are litmus paper or solution, phenolphthalein, China rose.


Fig. Litmus paper                      Fig. China rose

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