Question

Riya performs two set of experiments to study the length of the foam formed which
are as follows:
Set I: she takes 10 ml of distilled water in test tube “A” and adds 5-6 drops of liquid
soap in it and shakes the test tube vigorously.
Set II: she takes 10 ml of distilled water in a test tube “A” and adds 5-6 drops of
liquid soap with half spoonful of CaSO4 in it and shakes the test tube. Write your
observation and reason.

Answer 1

 bcoz it is soft water and soft water forms lather . set 1 gives lengthy foam                                                                                                                                                                                                                                                       

Answer 2

In the set I large amount of foam will be produced as water is soft. But  in set II very less amount of foam will be produced as calcium sulphate is added to water so water becomes hard.