Question

Explain the following observations:

1. Water wets glass surface but does not wet the waxed glass surface. 
2. A steel needle placed carefully on the surface of water does not sink.

Answer 1

1. Water wets glass surface but does not wet the waxed glass surface. 
   • water wets glass-adhesive force is stronger between water molecules and glass molecules.
      
2. A steel needle placed carefully on the surface of water does not sink. 
   • surface of water acts/appears like an elastic stretched 2km due to forces of surface    tension.