Question

Oil floats on water. The most accurate reason for this is,
A. Oil is less dense than water
B. Oil is immiscible (does not dissolve) in water
C. Oil is both less dense and immiscible with water
D. Water is heavier than oil

Answer 1

Hint: Even though oil and water are liquids they differ in many properties. They differ in density, viscosity, polarity etc. These differences can be a reason why oil floats on top of water.

Complete step by step answer:
Water and oil have different densities. Water has more density than oil. There exists a strong attraction between the water molecules. The water molecules are attracted to each other through intermolecular hydrogen bonds. Water is polar. Polarity allows them to form strong hydrogen bonds.
Oil is not polar. There is a concept called dissolves like. According to this concept, polar molecules dissolve in polar solvents. In non-polar solvents, polar molecules do not dissolve. Also non-polar molecules do not dissolve in polar solvents. Hence when oil is added to water, they do not mix. Instead oil and water from two separate layers. This is because oil is nonpolar and it is not attracted to water molecules.
Anything having density less than that of water will float on the top of the water layer. Oil always floats on water. The reason behind this is, oil is less dense than water.
Hence the correct answer is option C, Oil is both less dense and immiscible with water. Both the density and immiscibility of oil can be the reason.

So, the correct answer is Option C.

Note: Oil is hydrophobic in nature. Hydrophobic means “fear of water”. Instead of being attracted to water they are repelled from the water molecules. The molecules which are attracted to water are called hydrophilic.