Properties of Liquids Surface tension is the resistance of a liquid to an increase in its surface area. Strong intermolecular forces (polar molecules)

Properties of Liquids

Surface tension is the resistance of a liquid to an increase in its surface area.Strong intermolecular forces (polar molecules)

High surface tension

To increase a liquid’s surface area, molecules must move from the interior of the liquid to the surface. Requires energy since intermolecular forces must be overcome.


Cohesion is the intermolecular attraction between like molecules

Adhesion is an attraction between unlike molecules

Adhesion

Cohesion

attracted to glass

attracted to each other

Capillary action – spontaneous rising of a liquid in a narrow tube.


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

Strong intermolecular forces

High viscosity

Two categories

•Amorphous solids – considerable disorder in their structures.

•Crystalline solids – highly regular arrangement of their components.•Lattice – three dimensional system of points designating the positions of the components that make up the crystal.•Unit Cell – smallest repeating unit of a lattice.

At lattice points:

• Atoms

• Molecules

• Ions

Unit cells in 3 dimensionsUnit Cell

latticepoint

Types of Crystalline Solids

Ionic Solids – Ion-Ion interactions are the strongest (including the “intermolecular forces” (H bonding, etc.)

• Lattice points occupied by ions• Held together by electrostatic attraction• Hard, brittle, high melting point• Poor conductor of heat and electricity

CsCl ZnS CaF2


Network Atomic Solids – Stronger than IM forces but generally weaker than ion-ion

• Lattice points occupied by atoms• Held together by covalent bonds• Hard, high melting point• Poor conductor of heat and electricity

diamond graphite

carbonatoms


Metallic Atomic Solid – Typically weaker than covalent, but can be in the low end of covalent

• Lattice points occupied by metal atoms• Held together by metallic bonds• Soft to hard, low to high melting point• Good conductors of heat and electricity

Cross Section of a Metallic Crystalnucleus &inner shell e-

mobile “sea”of e-


Molecular Crystals• Lattice points occupied by molecules• Held together by intermolecular forces• Soft, low melting point• Poor conductor of heat and electricity

Sulfur crystals

Phosphoruscrystals

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Properties of Liquids Surface tension is the resistance of a liquid to an increase in its surface area. Strong intermolecular forces (polar molecules)