Properties of liquids : Viscosity


Viscosity is the resistance to flow that is exhibited by all liquids and gases.The viscosity of a liquid can be obtained by measuring  the time it takes for a  given quantity to flow through a capillary tube.

In everyday terms (and for fluids only), viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey  is "thick", having a higher viscosity. Put simply, the less viscous the fluid is, the greater its ease of movement.So, a liquid's resistance to flow is called its viscosity,the greater the its viscosity ,the more slowly liquid pours.

Viscosity measures how  easily molecules slide by one another and this depends strongly on molecular shapes.Liquids such as water acetone and benzene whose molecules are small and compact ,have low viscosity.In contrast large molecules such as sugars in honeyand the hydrocarbons found in oils tend to be tangled up with each other.Tangling inhibits the flow of molecules and leads to high viscosity.

Temperature effect on viscosity : molecules move faster as temperature increases and this allows them to slide by one another more easily.And dependence is quite noticeably for highly viscous substabces such as honey and syrup,which are much easier to pour when hot than when cold.