Mechanical Properties of Fluids

Surface Tension


  • Work done per unit area in increasing the surface area of a film is known as surface energy.
  • Every liquid surface behaves like an elastic membrane and surface tension is a molecular phenomenon.
  • Surface tension can also be defined as the surface energy per unit surface area.
  • Angle of contact is the angle made by the tangent drawn to the liquid surface at the point of contact of solid liquid surface.
  • Angle of contact is not changed by the inclination of solid object in liquid.
  • The rise or fall of a liquid in a capillary called capilarity it is due to surface tension.
  • If the angle of contact is greater than 90° then the liquid does not wet solid and capillary depression takes place.
  • If the angle of contact is less than 90° then the liquid wets solid and capillary rise takes place.
  • Surface tension decreases with the increase of temperature.
  • Weakly soluble impurities decrease surface tension and highly soluble impurities increases surface tension.

Surface Tension View the Topic in this video From 23:01 To 1:01:20

Disclaimer: Compete.etutor.co may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. Compete.etutor.co makes no representations whatsoever concerning the content of these sites and the fact that compete.etutor.co has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by compete.etutor.co with respect to such sites, its services, the products displayed, its owners, or its providers.

1. The property of a liquid by virtue of which it tries to acquire minimum surface area is called surface tension. It is given by surface tension, \tt S=\frac{F}{l}

2. Surface energy of a given liquid surface is equal to the work done against the force of surface tension, in forming the liquid surface of given area at a constant temperature.
Surface energy, E = S × ΔA