Which material is cited as a suitable medium for coalescing oil droplets?

• A. Aluminum
• B. Teflon
• C. Glass
• D. Wood

Answer: (B)

Coalescing oil droplets work best on surfaces that don’t wet easily and don’t strongly hold onto the droplets. A low-energy, non-stick material like Teflon (PTFE) provides a very smooth, non-wetting surface, so oil droplets can move together, meet, and merge into larger droplets rather than sticking individually to the surface. This promotes efficient coalescence and separation.

In contrast, materials with higher surface energy or rough textures—like aluminum, glass, or wood—tend to cause droplets to cling or pin, or trap oil within pores, which hinders the droplets from coming together and coalescing as readily.