Which statement correctly describes the ends of a detergent's surfactant molecule?

• A. Both ends are attracted to water
• B. One end is attracted to water and the other end is attracted to oil
• C. One end is attracted to water and the other end is attracted to oily substances
• D. One end is attracted to oil and the other to water

Answer: (C)

Surfactants in detergents are amphiphilic, meaning they have a hydrophilic head that loves water and a hydrophobic tail that loves oils. At an oil–water interface, the molecule positions itself so the water-loving end is in the water and the oil-loving end is in the oil. This dual affinity is what lets the detergent interact with both water and greasy substances, helping to break up and suspend oils so they can be rinsed away. That’s why the statement describing one end attracted to water and the other end attracted to oily substances is the best description. If both ends only liked water, grease wouldn’t be addressed; if both ends liked oil, there’d be no interaction with water to carry the oil away. The phrasing about oily substances broadens the idea to greases and oils commonly encountered.