RRB Group D 27 Nov 2025 Shift 1 Solved Paper

Concept: Micelles are clusters of soap molecules that encapsulate grease and dirt, enabling their removal by water.Explanation: Soap molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. In water, these molecules aggregate into spherical structures called micelles, with the tails pointing inward and the heads outward. The hydrophobic tails attract and surround non‑polar substances like oil and grease, trapping them inside the micelle. The hydrophilic heads remain in contact with water, making the micelle water‑soluble. When rinsed, the entire micelle – containing the trapped dirt – is washed away. This is the primary cleansing mechanism of soap. Micelles do not reduce water hardness, nor do they increase surface tension; in fact, soap lowers surface tension. Lather formation is a secondary effect, not the main role of micelles in cleaning.Answer: To trap and remove oil and dirt from clothes.