BECE Science 2020 Paper

Concept:Hard water contains dissolved $\mathrm{Ca}^{2+}$, $\mathrm{Mg}^{2+}$, or $\mathrm{Fe}^{3+}$ salts that prevent soap from lathering, whereas soft water is free from these salts and lathers easily.Explanation:Soft water lathers readily with soap because it does not contain dissolved calcium, magnesium, or iron salts.Hard water reacts with soap to form an insoluble scum, wasting a large amount of soap before any lather appears.Therefore, soft water saves a lot of soap when used for washing.Option A is incorrect because strong bone formation is linked to calcium minerals, not to the softness of water.Option B is incorrect because soft water is not known to prevent heart diseases.Option C is incorrect because soft water does not necessarily have a pleasant smell or taste.Answer:D. saves a lot of soap when used in washing