Aula #15

Intermolecular Forces Liquids and Solids

& at the surface

Surface tension ….is the amount of energy required to stretch or increase the surface of a liquid by a unit area.

Strong intermolecular forces > High surface tension

Surface tension ….is the amount of energy required to stretch or increase the surface of a liquid by a unit area.

Strong intermolecular forces > High surface tension

Strong intermolecular forces > High surface tension

SurfactantSodium Laureth Sulfate

Change of the surface tension.. Presence of a surfactant

SurfactantSodium Laureth Sulfate

Strong intermolecular forces > High surface tension

SurfactantSodium Laureth Sulfate

Surface tension ….is the amount of energy required to stretch or increase the surface of a liquid by a unit area.

Bubble pressure tensiometer

Intermolecular Forces Liquids and Solids

& at the surface

Capillarity Cohesion is the intermolecular attraction between like molecules

Adhesion is an attraction between molecules in a different surface

Intermolecular Forces Liquids and Solids

& at the surface

Capillarity Cohesion is the intermolecular attraction between like molecules

Adhesion is an attraction between molecules in a different surface

Intermolecular Forces Liquids and Solids

& at the surface

Capillarity Cohesion is the intermolecular attraction between like molecules

Adhesion is an attraction between molecules in a different surface

Capillarity Cohesion is the intermolecular attraction between like molecules

Adhesion is an attraction between molecules in a different surface

Intermolecular Forces Liquids and Solids

& at the surface

Wetting (molhabilidade)

Contact angle,

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity is a measure of a fluid’s resistance to flow.

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity is a measure of a fluid’s resistance to flow.

Shearing flow is opposed by friction between adjacent layers of fluid (which are in relative motion).A force is required to sustain the motion of the upper plate. The relative strength of this force is a measure of the fluid’s viscosity.

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity is a measure of a fluid’s resistance to flow.

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity function (dynamic viscosity over shear rate):

1 ... Newtonian liquid

2 ... shear-thinning substance

3 ... shear-thickening substance

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity temperature /pressure dependence

EQUATION

Vogel–Tammann–Fulcher (VTF)

Viscosity pressure

Viscosity temperature

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity type of flow

In laminar flow, molecules move in orderly layers,

while in turbulent flow they follow no pattern

Intermolecular Forces Liquids and Solids

& transport properties

Viscosity type of flow …. Reynolds NUMBER Re

In laminar flow, molecules move in orderly layers,

while in turbulent flow they follow no pattern