Explanation:
Hard water contains dissolved Ca²⁺ and Mg²⁺ ions which react with soap to form insoluble scum, preventing lather. Soft water lathers readily. Distilled water is pure (soft). Rainwater is naturally soft but may dissolve CO₂ and become slightly acidic.
Explanation:
Detergents with branched hydrocarbon chains (ABS) resist bacterial degradation and persist in water bodies causing foam and pollution. Linear alkylbenzene sulfonates (LAS) are biodegradable and preferred. Soap is biodegradable but forms scum with hard water. Sodium lauryl sulfate is used in shampoos and is biodegradable. Environmental regulations now mandate the use of linear chain detergents.
Explanation:
Iodine directly converts from solid to violet vapor on gentle heating (sublimation). NaCl melts; sugar decomposes; copper melts at high temperature. Other sublimable substances: camphor, naphthalene, dry ice.
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