Why does oil float on water?

• A. Because oil is polar and water is nonpolar.
• B. Because oil is more viscous than water.
• C. Because oil has a lower density than water.
• D. Because oil molecules are larger than water molecules.

Answer: (C)

Verified step by step guidance

1. Understand the concept of density, which is defined as mass per unit volume, mathematically expressed as \(\text{density} = \frac{\text{mass}}{\text{volume}}\).
2. Recognize that substances with lower density will float on substances with higher density when they are immiscible (do not mix).
3. Recall that water is a polar molecule with a relatively high density (about 1 g/cm³), while oil is generally nonpolar and has a lower density than water.
4. Since oil has a lower density than water, it is less heavy per unit volume, causing it to float on top of water rather than sink.
5. Note that polarity, viscosity, and molecular size do not directly determine whether a substance floats or sinks; density is the key factor in this context.