Question

would you be able to check if water is hard by using a detergent

Answer 1

heya
yes we can check because detergent forms lather even with hard water where as soap does not form lather.soap only gives out scum.
hope it helps

Answer 2

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Detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check if water is hard; by using a detergent.