Viscosity, Kinematic viscosity, Compressibility, Surface tension and capillarity are most important properties of liquid. The following properties of liquid are important from the subject point of view

1. Viscosity. It is also known as absolute viscosity or dynamic viscosity. lt is defined as the property of a liquid which offers resistance to the movement of one layer of liquid over another adjacent layer of liquid. The viscosity of a liquid is due to cohesion and interaction between particles.

2. Kinematic viscosity. It is defined as the ratio of dynamic viscosity to the density of liquid.

3. Compressibility. It is that property of a liquid by virtue of which liquids undergo a change in volume with the change in pressure. The compressibility is the reciprocal of bulk modulus of elasticity, which is defined as the ratio of compressive stress to volumetric strain.

4. Surface tension. It is that property of a liquid which enables it to resist tensile stress. It is denoted by sigma. It is expressed in N / m.

5. Capillarity. It is defined as a phenomenon of rise or fall of a liquid surface in a small vertical tube held in a liquid relative to general level of the liquid. The height of rise or fall (h) in the tube is given by

where

sigma = Surface tension,

alpha = Angle of contact of the liquid surface,

w = Specific weight of liquid, and

d = Diameter of the capillary tube.