1What is an indicator? Write the names of three common indicators.
2On what basis does an indicator separate different substances into acid, base and salt?
3Complete the table of the colours indicators show in acid, base and salt.
4Explain how red litmus paper can be made from a flower.
5A piece of cloth stained with turmeric turns red when it is washed with soap. Why?
6Prepare a list of any three local things that are used to make natural indicators.
7Why does a laboratory keep two colours of litmus paper when both rows of the table are the same?
8Why can phenolphthalein never tell an acid from a salt?
9Orange juice, washing soda and salt water are in three bottles. How would you separate them with red and blue litmus paper?
10Taste is also a kind of indicator. Why has it been replaced by paper in the laboratory?