Why does oil not dissolve in water but floats on its surface?a)Oil mol...
Oil does not dissolve in water because oil molecules are non-polar, while water molecules are polar. This difference in polarity causes oil and water to repel each other. When oil is mixed with water, the oil molecules clump together to minimize contact with water molecules, forming droplets that float on the water's surface. This phenomenon is due to the hydrophobic nature of oil, which avoids interactions with the polar water molecules. This property is also why oil spills on water create slicks that spread out rather than mixing uniformly with the water.
Why does oil not dissolve in water but floats on its surface?a)Oil mol...
Why Oil Does Not Dissolve in Water
The reason oil does not dissolve in water but instead floats on its surface lies in the chemical structure of both substances.
Chemical Structure and Polarity
- Water is a polar molecule, meaning it has a positive and a negative end. This polarity allows water molecules to form hydrogen bonds with each other.
- Oil, on the other hand, is made up of non-polar molecules. These molecules do not have distinct positive or negative ends and do not form hydrogen bonds.
Repulsion Between Molecules
- Because of their differing polarities, oil molecules repel water molecules. This is often summarized by the phrase "like dissolves like," which means that polar substances are more likely to dissolve in polar solvents, and non-polar substances in non-polar solvents.
- When oil is introduced to water, the water molecules prefer to stick to each other rather than mix with the non-polar oil molecules. This leads to the formation of a distinct layer.
Density and Floating
- Additionally, oil is generally less dense than water, causing it to float on the surface. Density is another factor that contributes to this separation.
Conclusion
In summary, the correct answer is option 'B': Oil molecules repel water molecules due to their chemical structure. This fundamental difference in polarity and molecular interaction is the primary reason for the behavior observed when oil and water are combined.
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