Oil rising velocity in separation processes is affected by what property of the oil globules?

• A. Color
• B. Size in Microns
• C. Temperature
• D. Viscosity

Answer: (B)

Rising velocity of oil droplets in water is determined by the balance between buoyancy pulling the droplet upward and viscous drag resisting that motion. For small, spherical droplets, the terminal velocity follows a relation where velocity grows with the square of the droplet radius. In other words, larger droplets experience a greater buoyant force relative to the drag they experience, so they rise much faster. This makes the size of the oil globules the primary factor setting how quickly they ascend, measured in microns. Color has no physical effect on motion, and while temperature or the oil’s viscosity can influence drag, those relate to other properties or conditions rather than the droplet’s size itself. Therefore, the size of the oil globules best explains the rising velocity.