Surface Tension and Surface Energy
Surface Tension
Surface tension is a property of liquid which arises due to the different situation of the liquid molecules on the surface and in the bulk of the liquid.
A molecule lying inside (bulk) the liquid is surrounded by other molecules and so is attracted equally in all directions. Thus, the resultant force of attraction acting on the molecule is zero.
However, A molecule lying at the surface of liquid is attracted by liquid molecules from the bulk of the liquid and feel inward pull. As a result of this inward pull on all molecules lying at the surface, the surface behave as if it were under tension and the surface of the liquid tends to the smallest possible area for a given volume of the liquid. This gives the lowest energy state of the liquid.
Surface tension of a liquid is defined as the force in dyne acting at right angles to the surface along one cm length of the liquid surface.
unit of surface tension is dyne per centimetre or Newton per metre.
Surface tension is a property that arises due to the intermolecular forces of attraction among the liquid molecules. Greater the intermolecular force of attraction, higher is the surface tension of the liquid.
Surface tension of liquid generally decreases with increase of temperature and becomes zero at the critical temperature. Surface tension decreases with increase in temperature is due to on increasing the temperature, the kinetic energy of the molecules increases ,and, therefore the intermolecular attraction decreases.
Surface Energy
The work in ergs required to be done to increase or extend the surface area by one square centimeter is called surface energy.
The unit of surface energy is ergs per square centimeter or joules per square meter.
