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.
Properties of Liquids
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.
Properties of Liquids
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
Types of Crystalline Solids
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
Types of Crystalline Solids
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-
Types of Crystalline Solids
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