Question

how do you identify the hard water and soft water using soap​

Answer 1

Make separate soap solutions in two different beakers - one with soft water and other with hard water.

In one of the beaker, you will observe lather and in other one you will observe a white precipitate known as scum. The beaker in which scum has formed contains hard water.

Hope this will help you.

Answer 2

Hard water requires more soap or detergent for laundry or dishwashing, and can leave calcium carbonate deposits on shower heads, boilers, or pipes. while the soft water does not requires more soap or detergent for laundry or dishwashing, and does not leaves calcium carbonate deposits on shower heads, boilers, or pipes.