Question

Hard water produces less foam with detergent. Do you know why?

Answer 1

Answer:

this is because when a calcium and magnesium particle react with detergent molecule, the new substance does dissolved in water, so there is no scum.

If you add the same amount of soap in equal volume of soft water and hard water, you will get less foam in hard water. This is because the soap reacts with the calcium and magnesium ions in hard water and forms calcium and magnesium soaps. These are insoluble in water and gets deposited as scum. So part of the soap will not be available to make foam. Less available soap means less foam.