Explain the formation of scum when hard water is treated with soap. When hard water is treated with soap:Soap reacts with minerals like calcium and magnesium in hard water.This forms a sticky, insoluble substance called scum.Scum sticks to surfaces, making cleaning difficult.Scum also reduces the cleaning power of soap. Explore Entire Collection of Texcellency Books Download Your FREE Book Now “A good textbook is like a smart GPS — it doesn’t just give you the destination, it tells you every turn along the way, in simple language you actually understand.”