How does the viscousity of a liquid change with temperature

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How Does the Viscosity of a Liquid Change with Temperature

Theory

Viscosity is a measure of a fluid's resistance to flow when acted upon by an external force such as a pressure differential or gravity. Viscosity is a general property of all fluids, which includes both liquids and gases. It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion. The viscosity affects the size of liquid particles, increasing the viscosity tends to increase the size of liquid particles, which then increases their gravitational settling rates.

The viscosity of a liquid changes with temperature, as the temperature increases the viscosity decreases as the intermolecular forces weaken. Energy added to the system in the form of heat increases the kinetic energy of the molecules, with higher kinetic energy, the molecules are able to overcome the intermolecular attraction resulting in a less viscous liquid. If a ball bearing is dropped through liquid it very quickly reaches its terminal velocity, when it reaches terminal velocity it should then be going at a constant speed.

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Stokes Law can be used to calculate the viscosity of a liquid. The formula for Stokes Law is:-

vt = Terminal Velocity

r = Radius

q = Density of the ball bearing        

δ = Density of the liquid

μ = Viscosity

Density of the ball bearing-

Density of Liquid

Volume = 4/3or3

        

Depending on the velocity of the ball bearing, the motion of the liquid is different. These diagrams show the liquid molecules movement around the ball bearing when it is dropped.

 

At low velocities the liquid ...

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