Oil rises to the surface in water because of its specific gravity being

• A. Greater than water
• B. Very high viscosity
• C. Less than water
• D. Equal to water

Answer: (C)

Buoyancy dictates whether a substance sinks or rises in a liquid. A liquid that is less dense than water has a lower specific gravity, so the buoyant force on it (the weight of water it displaces) exceeds its own weight. Oil is less dense than water, with a typical density around 0.8 g/cm³ vs water’s about 1.0 g/cm³, giving a specific gravity less than 1. This makes oil float to the surface. If the oil were denser than water, it would sink; if it had the same density, it would be neutrally buoyant. Viscosity affects how fast it moves but not whether it rises or sinks.