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## Viscosity

### Viscosity Expresses How Viscous a Substance Is as a Number

Liquids can be free-flowing like water or gooey like honey, and viscosity represents how "free-flowing" or how "gooey" a liquid is.

Units of Viscosity
Pa•s (pascal-second) = 0.001
mPa•s (millipascal-second) = 1
cP (centipoise) = 1

#### Viscosity and Temperature-Viscosity Changes with Temperature-

As the temperature of a substance increases, the viscosity decreases. For example, everyone has likely already experienced that when honey is heated up it becomes less gooey (less viscous).

#### Kinematic Viscosity-Expressing the Liquid's Inability to Move-

Viscosity expresses how difficult it is for an object to move through a liquid. Conversely, kinematic viscosity expresses how difficult it is for the liquid itself to move. Viscosity represents the brakes put on the flow, but the effectiveness of the brake depends on the density of the fluid. This is the same as how a bicycle and a bus going the same speed and putting on the same strength of brake would still stop differently because of their difference in weight. Kinematic viscosity is calculated by dividing a substance's viscosity by its density. The unit for kinematic viscosity is m2/s.