Liquid State

Definition Of Liquid
State of matter with definite volume but not definite shape.

Behaviour Of Liquids:-
OR
Properties Of Liquid

1) No Definite Shape
Molecules of liquids have random motion due to which molecules changes theit position so the liquids have no definite shape.
2) Diffusion
Property of liquid to mix with each other is called diffusion of liquid.
Example
A drop of ink diffuses in the glass of water.
Diffusion is low in liquid than gasses due to closeness of molecules.

3) Compressibility
Property of liquid to be compressed by pressure is called compressibilityl.
Example
Brake oil is compressed in brakes of auto mobiles when driver passes the brake.
Due to very small space between the molecules of liquid are compressed by high pressure up to such a small extent that the volume does not show any marked change.

4) Contraction and Expansion:
When the liquid is cooled its molecule come close and the volume of the liquid is decrease this is called contraction. Again when the liquid is heated space between its molecules increase and the volume of the liquid increases this is called expansion of the liquid.

Viscosity:-

Definition:-
Resistance to flow of liquid is called viscosity. Its is represented by a symbol called eta.

Explanation:-
When the liquid are allowed to flow then the layers of liquid molecules are passes over each other due to which the friction take place between them which produce resistance in the flow of liquid this resistance in flow of liquid is known as viscosity.
Thus, the liquid which flow slowly, they have more resistance in flow means more viscosity and vice versa.
Example
Honey, mobile oil are more viscous than water and petrol so they flow slowly.
Unit of viscosity
Unit of viscosity is poise. Its S.I unit is
 Ns/m^2

Factors Affecting the Viscosity:-
Following the factors affect the viscosity.

1) Intermolecular Force Of Attraction
Greater the force of attraction between the molecules of a liquid more is the resistance in the flow of liquid thus more is the viscosity of the liquid and vice versa.

2) Temperature
By increasing temperature kinetic energy of the liquid molecules increases so the motion of molecules increases and the resistance in their flow of decreases due to the viscosity decreases and the vice versa.

3) Size of molecules and molecular mass:
Liquid with large size of molecules and more molecular mass have more resistance in the flow so their viscosity is more than the liquids will small size of molecules and low molecular mass.

4) Arrangement of molecules:
Liquids with irregular arrangement of molecules have more resistance in flow so their viscosity is more than the liquids with regular arrangement of molecules.

Surface Tension:-

Definition:-
Force per unit lenght acting on the surface of a liquid is called surface tension. It is denoted by the symbol gamma.

Explanation:-
Molecules of liquid attracts each other. Molecules of liquid in the bulk are attracted from all the sides by the molecules, thus they have a balance attraction.
But the molecules on the surface have attraction of inner molecules which pull them downward. This downward pull inmer molecules on the surface molecules  create a tension on the surface of liquid called surface tension.
Surface tension tends to reduce the surface area of a liquid and creates a membrane of liquid molecules on the surface of liquid called surface of the liquid.
Unit of surface tension:
Unit of surface tension is Dyne/cm,
erg/cm^2 and S.I unit is N/m

Factors affecting surface tension:-
Following factors affect surface tension.

1) Intermolecular Force of Attraction:
Greatee the force of attraction between the molecule of liquid more is the surface tension and vice versa.

2) Temperature:
By increasing temperature kinetic energy of liquid molecules increases so the force of attraction between the liquid molecules decreases due to whicu surface tension of the liquid decreases and vice versa.

Attraction Forces Of Liquid Molecules:
There are two types of force between molecules.

1) Cohesive force:
Force of attraction between the liquid molecules for each other is called cohesive force Or intermolecular force of attraction.

2) Adhesive force:
Attraction of liquid molecules with a solid phase is called adhesive force. Liquid which have high cohesive force, they have low adhesive force and the liquids having high adhesive force have low cohesive force.

Capillary action of a Liquid:
Raise or fall of a liquid in a capillary tube is called capillary action.
Explanation of Following reasons:

1) Water rises in capillary tube:
 Water molecules have high adhesive force with the walls of capillary tube due to which it form concave meniscud or surface with the walls of the tube which rises it in the capillary tube.

2) Mercury falls in the capillary tube:
Atoms of mercury have high cohesive force with each other than the adhesive force with the walls of capillary tube, due to which it forms convex meniscus or surface with the wall of tube and the convex meniscus suppress mercury in the tube so it falls in the capillary tubes.

3) Water is a wetting liquid:
Water has high adhesive force than cohesive force so it spreads on the surface of the substance on which it is applied and stick with the substance and wet the substance and wet the substance,
thus it is a wetting liquid.