Exp.4 Determination the Viscosity of Liquids

Exp.4 Determination the Viscosity of Liquids

Theory:
The viscosity of liquid is a resistance to flow of a liquid. All liquids appear resistance to flow change from liquid to another, the water faster flow than glycerin, subsequently the viscosity of water less than glycerin at same temperature. Viscosity occurs as a result of contact liquid layers with each other. The viscosity is measuring by Ostwald viscometer.
Relative Viscosity is the ratio of the absolute viscosity of the fluid on the viscosity of water at a certain temperature.……..>>>>>>>>>>>>>. .
The viscosity coefficient is force (dyne) necessary to move the layer of liquid 1 cm2 in speed 1 cm/sec on another layer of liquid and the distance between them is 1cm.
Equation the Poisellieh :
?=t (?r^4 f)/8vl
For two liquids:
?_1/?_2 =(f_1 t_1)/(f_2 t_2 )
Where:
(?r^4)/8vl is constant
When:
f=gdh
??_1/?_2 =(t_1 d_1)/(t_2 d_2 )
?_1 is viscosity of liquid 1.
?_2 is viscosity of liquid 2.
t_1 flow time of liquid 1.
t_2 flow time of liquid 2.
d_1 density of liquid 1.
d_2 density of liquid 2.
The factors effect on the viscosity:
Effect of Temperature: the temperature of the liquid fluid increases its viscosity decreases. In gases its opposite, the viscosity of the gases fluids increases as the temperature of the gas increases.
Molecular weight: the molecular weight of the liquid increases its viscosity increases.
Pressure: when increase the pressure on liquids, the viscosity increase because increase the attraction force between the molecules of liquid.