Question

The forces acting upon a drop a liquid placed on a horizontal surface is

Answer 1

Due to surface tension surface of water droplet is always in tension and behaves like stretched membrane.

Molecule lying in surface of the water droplet is pulled laterally and downward due to attracting forces of other molecules.

Operative on this molecule towards right and left is counter-balanced but downward pull remains unbalanced as there no molecule to balance upward.

This unbalanced pulling force operating on the surface molecules causes a tension pulling molecules inwards.  

This inward pull operating on surface molecules tends to give minimum surface area to a liquid.