Answer: hard water.
- A hot water only
- B hard water
- C distilled water only
- D acidic water only
Correct answer: B. hard water
Explanation: Detergents do not form insoluble scum with the Ca²⁺/Mg²⁺ ions of hard water, so they still lather.
The hydrophobic hydrocarbon tail of each soap/detergent molecule dissolves into an oily dirt droplet, while the hydrophilic (ionic) head stays in the surrounding water - trapping the grease inside a micelle that rinses away with water.
Concept context
Drugs and how they interact with biological targets, chemicals in food, and cleansing agents (soaps and detergents) - chemistry applied directly to daily life and healthcare.