Q.Explain : mechanism of cleansing action of soap with flow chart.

Step 1. The starting problem. Section 16.3.2 states dirt on a surface is held there by a film of oily matter, and because oil does not dissolve in water, plain water alone cannot remove it.

Step 2. The molecule's two parts. Every soap/detergent molecule has a polar hydrophilic head, which dissolves in water, and a long nonpolar hydrophobic tail, which dissolves in oil/grease.

Step 3. Micelle formation around the dirt. When applied to the greasy surface, these molecules arrange themselves around an oily dirt droplet so that every hydrophobic tail points inward, into the oil, while every hydrophilic head points outward, into the surrounding water -- this arrangement is shown in Fig. 16.2 and is called a micelle. …

Walking through the head/tail-orientation micelle mechanism of Section …

• Describing soap as 'dissolving' the dirt directly, rather than the correct micelle mechanism, where the dirt is encapsulated and carried away, not chemically dissolved. …