A high wetting angle indicates the surface is not wettable, making it hydrophobic.

A high wetting angle indicates the surface is not wettable, making it hydrophobic.

• A. Hydrophobic
• B. Hydrophilic
• C. Wettable
• D. Non-wettable

Answer: (A)

Wettability hinges on the contact angle between a liquid and a solid. A high wetting angle means the liquid does not spread and tends to bead up on the surface. That behavior is the hallmark of a hydrophobic surface—water-repelling and not easily wetted. Hydrophilic describes the opposite, with a low contact angle and good spreading of the liquid. Wettable refers to surfaces that the liquid can wet easily, while non-wettable is a broader description but the precise term for high-angle behavior is hydrophobic.

Wettability hinges on the contact angle between a liquid and a solid. A high wetting angle means the liquid does not spread and tends to bead up on the surface. That behavior is the hallmark of a hydrophobic surface—water-repelling and not easily wetted. Hydrophilic describes the opposite, with a low contact angle and good spreading of the liquid. Wettable refers to surfaces that the liquid can wet easily, while non-wettable is a broader description but the precise term for high-angle behavior is hydrophobic.