What is surface tension of liquids? Explain the affect of temperature on the surface tension of liquids.

Explanation

The phenomenon of surface tension is due to the existance of strong intermolecular forces of attraction in liquids.

Consider a molecule (A) lying somewhere inside the liquid. This is attracted equally to all directions by other molecules surronding it. So the net resultant force of attraction acting on this molecule is zero. This is true for all molecules present inside the body of the liquid. Now consider a molecule lying at the surface of the liquid (B). This is attracted by large number of molecules lying in the bulk of the liquid than by very few molecules lying above in the vapour phase. Thus a molecule at the surface experiences a net inward attraction. THis is true for all molecules lying at the surface As a result of the inward pull on all molecules lying at the surface, is not same. The surface behaves as if it were under tension like a stretched membrane. Hence this property of liquids is called surface tension.
The surface tension of a liquid is defined as " The force acting at right angle to the surface along unit length of the surface". IT is represented by v.
Examples:
1) The liquid drops are spherical. due to surface tension. (For a given volume of liquid, sphere has the minimum surface area).
2) At the crictical temperature of liquids, the surface tension is zero.
3) The rise of liquid in a capillary tube is due to surface tension.