Viscosity
This is the internal friction which exists between the layers of fluid in motion.
When water flows through a pipe, the velocity is not uniform through the pipe. The velocity is greater at the centre and less at the edge. The resistance of flow is smaller through a large pipe than through a small pipe. It is good to note that a viscose liquid flows through a pipe at a slower rate than a less viscose liquid. This is possible due to the frictional force in the liquid. The frictional force which slows down the movement of a ball through the liquid is called viscosity.
Experimentally, the frictional force f in the liquid is proportional to the viscosity of the liquid, the radius a, of the ball and the velocity v, at the ball in falling through the liquid.
f av
Viscosity opposes motion in the liquid, depend on relative velocity, the area of the surfaces in contact and on the nature of the liquid.
Surface tension
There are two forces that act on a liquid when the liquid is a t rest or in motion. When the liquid is at rest, we have viscosity.
With this we can say that surface tension is a force at the surface of liquid which acts as if there is a skin at the top. E.g. a needle placed gently on the surface of water, a small insect walking on the surface of water, umbrella.
Crystal structure
Characteristics of crystals
Some solids that possess definite melting points are called crystals. They have definite shapes as shown above. Crystals with the same crystalline shape are said to be isomorphous e.g. NaCl and alum. They are usually soluble in water.
Another type of structure is amorphous which is the opposite of crystalline substances i.e. they have no definite shape, they are all insoluble.
The ions and atoms in a crystalline substance are finely arranged unlike in an amorphous substance.
Elastic properties of solids
There is a law……
