No, used motor oil is not heavier than water. It's actually less dense, meaning it weighs less for a given volume. This is why oil floats on water.
Why Oil Floats: Density and Buoyancy
The key factor determining whether oil floats or sinks is its density. Density refers to how much mass is packed into a given volume. Water has a higher density than oil. Because oil is less dense, it experiences a buoyant force greater than its weight, causing it to float. This is illustrated by the fact that oil molecules are larger and cannot pack as tightly together as water molecules, resulting in lower density.
Several sources confirm this:
- Reference 1: Explicitly states that oil is lighter than water and floats because of its lower density.
- Reference 2 (Quora): Clearly states that oil is less dense than water and floats because it weighs less.
- Reference 3 (Reddit): A user mentions forgetting that oil is not heavier than water.
- Reference 10 (BobIsTheOilGuy): Confirms that the density of oil is different from water.
While some references mention the viscosity (thickness) of oil, this is a separate property and doesn't affect whether it floats or sinks. Viscosity influences how easily oil flows, not its relative density compared to water.
Practical Implications
Understanding that oil is less dense than water has several practical implications:
- Environmental Concerns: Oil spills on water will float on the surface, making containment and cleanup efforts crucial.
- Automotive Applications: The lower density of oil is a factor in engine lubrication and cooling system design.
