(i) Formation of Micelles:
Soap molecules have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. When soap is applied on oily dirt, the hydrophobic tails dissolve into the oil/grease, while the hydrophilic heads remain in water. Soap molecules arrange themselves around the oil droplet forming a micelle.
Diagram:
```
Water
↑↑↑↑↑ ← Hydrophilic heads (–)
||||
[OIL] ← Hydrophobic tails inside
||||
↑↑↑↑↑
Water
```
(Circular cluster: tails pointing inward toward oil, heads pointing outward toward water)
The micelle keeps oil suspended in water and is washed away easily.
---
(ii)
(1) Foam will be more in test tube Y (detergent).
Detergents work effectively in hard water because they do not react with calcium or magnesium ions present in it, so they continue to produce foam freely.
(2) A curdy white solid (scum) is formed in test tube X (soap).
Soap reacts with calcium and magnesium salts present in hard water to form an insoluble precipitate called scum (curdy solid). This reduces soap's cleansing ability and produces no lather.
---