Effect of temperature on viscosity of liquids.

Viscosity of liquids decrease as temperature rise. This inverse relationship is described by the following exponential equation:

Where η is absolute viscosity, A is a constant, Ea is activation energy required to initiate flow between liquid molecules, R is gas constant (equal to 1.9872 calorie/ (degree × mole) ), and T is temperature in Kelvin.
The following example plot shows how viscosity of glycerin changes from about 12000 cp at 0 °C (273 Kelvin) to about 600 cp at 30 °C (303 Kelvin).

From the exponential fit of the above plot we can find A and Ea as the following:
Y = (1.08 × 10^-9) × e^{(8200) x}

Where Y stands for viscosity in centipoise (cp) and x stands for 1/temperature in 1/Kelvin.
A = 1.08 × 10^-9
(Ea/ R) = 8200, Ea = 8200 × R, Ea = 8200 × (1.9872 cal/ (degree× mole).
Ea = 16295 cal/ mole.


Related posts:
What is rheology?
Definition and explanation of viscosity.