The knowledge of surface tension is applied in the following areas except in

Analyze the question: We need the one situation where surface tension is NOT involved.

Concept: Surface tension is the property of a liquid surface that makes it behave like a stretched elastic skin. It comes from the cohesive forces between molecules at the surface. It explains:

• Water forming droplets
• Light objects floating on water
• Soap and detergents lowering surface tension so water can wet and clean surfaces
• Waterproof materials resisting wetting

Checking each option:

• A. Manufacturing of rain coats: Surface tension is involved. Raincoat fabric is treated so that water does not wet it. Water forms droplets on the surface because of surface tension and the large contact angle, and the droplets roll off. ✔ (applies)
• B. Production of palm oil: This is mainly extraction by pressing, boiling, and clarification, which are mechanical and heat processes. It is not an application of surface tension. ✘ (the exception)
• C. Floating of a needle on water: This is the classic demonstration of surface tension. The surface film supports the needle's weight. ✔ (applies)
• D. Washing plates with soapy water: Soap reduces the surface tension of water. The water spreads and wets the plate better, and grease is emulsified. ✔ (applies)

Answer: The question asks for the exception, so the answer is B, production of palm oil.

Exam tip: For "except" questions, test each option against the concept and eliminate the ones that clearly apply. Associate surface tension with droplets, floating needles or insects, soap and detergents, and waterproofing. Anything outside those, like palm oil extraction, is probably the exception.