A drop of oil placed on the surface of water spreads out. But a drop of water place on oil contracts to a spherical shape. Why ?

Explanation

(i) A drop of oil placed on the surface of water spreads. Since the force of adhesion between the water molecules and oil molecules dominates the cohesive force of the ol molecule. So oil drop in water spreads.
(ii) The cohesive force of water molecule dominate the adhesive force between water oil molecules. So drop of water contracts to spherical shape.