Chemistry, asked by puravipao, 1 year ago

How determined the viscosity of ethanol with the help of Ostwald viscometer

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Answered by dqnish3720pd2puu
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Viscosity is an important property of fluids which describes a liquids resistance to flow and is related to the internal friction within the fluid. The most common type of flow behavior is shear flow where layers of fluid move relative to each another in response to a shearing force. This external force takes the form of a shear stress which is defined as the force acting over a unit area of fluid and results in a velocity gradient across the thickness of sample termed the shear rate. The shear viscosity or dynamic viscosity related to this process is given by the ratio of the shear stress to the shear rate as illustrated below. 



Non-Newtonian fluids

Many simple fluids are classed as Newtonian meaning their viscosity is independent of the amount of shear applied. Examples would be water and simple hydrocarbons. As fluid complexity increases, for example by the inclusion of bubbles, droplets, particles or polymers, fluids may take on more complex behavior and show a non-Newtonian response, where viscosity depends on the amount of applied shear. These types of fluids are generally called structured fluids or complex fluids and their behavior can be better described using a rheometer which can measure a range of viscosities over a wider range of shear rates, shear stress and temperature than a simple viscometer. 

Such non-Newtonian behavior is common for many industrial and commercial products including toothpaste, mayonnaise, paints, cosmetics and cements, which are generally shear thinning fluids, where viscosity decreases with increasing shear rate, although shear thickening can occur in some very structured fluids. 

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