What property of a duck's feathers causes them to repel water?

• A. The high cohesion between water molecules and feather proteins
• B. The adhesion of water molecules to the feather surface
• C. The capillary action within the feather structure
• D. The presence of hydrophobic molecules on the feather surface

Answer: (D)

Verified step by step guidance

1. Understand the concept of hydrophobic molecules: Hydrophobic molecules are nonpolar and repel water because they do not form hydrogen bonds with water molecules. This property is key to water repellence.
2. Recognize the role of hydrophobic molecules in duck feathers: Duck feathers are coated with oils or waxes that are hydrophobic, meaning they repel water and prevent it from soaking into the feathers.
3. Compare hydrophobicity with other properties: High cohesion between water molecules, adhesion to surfaces, and capillary action are properties of water itself, but they do not explain the water-repelling nature of duck feathers.
4. Relate hydrophobic molecules to water repellence: The hydrophobic coating on the feather surface creates a barrier that prevents water from adhering to or penetrating the feathers.
5. Conclude that the presence of hydrophobic molecules on the feather surface is the correct explanation for why duck feathers repel water.