What is the surface energy ? Find the relation between surface tension and surface energy. Explain why. (i) surface tension ofa liquid is independent of the area of the surface. (ii) detergents should have small angle of contact.

What is the surface energy ? Find the relation between surface tension

1.	What is the surface energy ? Find the relation between surface tension and surface energy. Explain why. (i) surface tension ofa liquid is independent of the area of the surface. (ii) detergents should have small angle of contact.
Answer» Solution :1st part: N/A 2nd part: (i) Surface tension of liquid is the force acting PER unit length on a line drawn TANGENTIALLY to the liquid surface at rest. Since this force is independent of area of liquid surface. Hence surface tension of a liquid is ALSO independent of the area of the liquid surface. (ii) A CLOTH has narrow spaces in the form capillaries. The rise of liquid in a capillary tube is directly proportional to `cos theta`. If `theta`is small , `cos theta` will be LARGE. Due to this detergent. s penetration in the cloth will be better. Hence, detergents should gave small angle of contact.