Question

EXPLAIN : water on clean glass surface, tends to spread out,while mercury on the same surface tends to form a drop ??

Answer 1

mercury density is higher and it is more viscous than water

Answer 2

The gravitational force tries to flatten out the fluid onto the surface.On the other hand, surface tension and internal fluid pressure are trying to form a spherical structure. Water has very weak surface tension compared to mercury. Also, water has high tendency to stick and spread onto other surfaces while is zero/negligible in mercury. Hence the observation.