Multiple choice

The effectiveness of soap is reduced, when it is used in _______ .

  1. cold water

  2. warm water

  3. soft water

  4. hard water

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hard water contains dissolved calcium and magnesium ions that react with soap to form an insoluble precipitate known as scum. This prevents the soap from forming a lather, thereby reducing its cleaning effectiveness.