Why does oil float on water?

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

Answer: (A)

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 when two liquids are immiscible (do not mix), the one with the lower density will float on top of the one with the higher density.
3. Recall that water has a density of approximately 1.00 g/cm³ at room temperature, while most oils have densities less than 1.00 g/cm³.
4. Note that the polarity of molecules affects solubility but does not directly determine whether one liquid floats on another; water is polar and oil is nonpolar, which causes them not to mix, but the floating behavior depends on density.
5. Conclude that oil floats on water because oil has a lower density than water, causing it to stay on top rather than mixing or sinking.