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

Answer: (D)

It remains spherical

When a water drop falls on the surface of oil, 2 forces come into play. 1 being the cohesion forces within the water molecules and the other being the adhesion forces between oil and water.

Now, as we all know that oil is hydrophobic in nature, as a result the adhesive forces between oil and water are much weaker compared to the cohesive forces between water and water.

Therefore, the water drop has a tendency to maintain its spherical shape in order to minimize the surface energy.