8.3 Viscosity, Adhesion, and Cohesion

What is viscosity?



some fluids are thicker or thinner than others.
ex: water is thinner than honey.
ex:Molasses is thicker than vegetable oil.


The thinness or thickness of a liquids a property of fluids called vicosity.


Viscosity describes a fluid's resistance to flow.
A thick liquid has a greater viscosity than a thin liquid.
The thicker liquid is more resistant to flow.



How do heating and cooling affect viscosity?


To compare the vicosity of fluids, you can measure their fow rate.

Flow rate: The speed at which a fluid flow from one point to another.
ex: honey is more viscous than water, the flow rate of honey is slower than water.

If honey is heated, the particles that make up honey move farther apart.
Now the honey is more viscous than it was before.

If gas is heated, the particles that make up the gas move faster.
Heating a gas increase its viscousity.

• When the viscosity of a fluid decreases, its flow rate increase.
• You can compare the viscosity of different fluids by comparing their flow rate.
• Flow rate is also affected by adhesion and cohesion.
• The slower the fluid flows, the greater the viscosity.

What is cohesion?

The property fluids that makes the particles hold together because they are attracted to each other is called cohesion.

ex: The water drop takes the shape of a disc.

The water particles at the surface attract each other in a way that makes the surface act like a skin. This effect is called surface tension.

What is adhesion?

Adhesion is the attraction between particles of a fluid and another substances so that the fluid clings to it.