Question

When a drop of water is dropped on oil surface, then:
A.It will mix up with oil
B.It spreads in the form of a film
C.It will deform
D.It remains spherical

Answer 1

Hint:To solve this problem make use of the definition of cohesive force and adhesion force.

Complete step-by-step solution:
Here,
We know that,
When a drop of water happens on the oil surface two forces come into play. Within the water molecules, one is the cohesion forces and the other is the adhesion forces between oil and water.
Now, as we all know that, oil is hydrophobic, as a result of which the adhesive forces between oil and water are much weaker than the cohesive forces between water and water.
Therefore, water drop helps to retain its spherical shape such that surface energy is minimised.
Hence,
The correct answer is (D) which is that it remains spherical.

Note: Cohesive forces are responsible for the surface tension, a phenomenon that results in a liquid’s surface propensity to resist rupture when put under stress.
Adhesion is the tendency to adhere to each other for dissimilar particles or surfaces (cohesion refers to the tendency to adhere to each other for similar or identical particles / surfaces). Many kinds of forces that cause adhesion and cohesion can be categorised.
The physical property of a molecule, evidently repelled by a mass of water, is hydrophobicity. In addition, the hydrophilic are attracted to water. Hydrophobic molecules tend to be non-polar, and thus prefer neutral as well as non-polar solvent.