What causes water to be classified as hard water?

Explanation

Hard water contains relatively high levels of dissolved calcium and magnesium salts, usually picked up as water passes through mineral deposits like limestone. This mineral content makes it harder for soap to lather effectively and can lead to scale buildup inside pipes, kettles, and water heaters over time. Water softening treatments typically work by replacing these calcium and magnesium ions with sodium ions. Explore more Everyday Science MCQs on mcqstutor to keep practicing.