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12-3 Liquids and Solids
•Liquids
•The kinetic theory also can be used to explain liquid
and solid behavior.
•Liquids have attractive forces between molecules
and as the temperature (KE) decreases, the forces
win and cause the molecules to move around each
other freely, but stick together as a liquid.
•Liquids are considered incompressible.
•Liquids take the shape of their container, but unlike
gases do not expand to fill their container.
Viscosity
•Viscosity is the resistance, of a liquid to flow.
•Syrup flows slower than water…syrup has a high
viscosity.
•In liquids, the stronger the intermolecular forces, the
higher the viscosity.
•The larger a molecule, generally the higher the
viscosity…long chain molecules have high viscosity.
•Viscosity decreases with an increase in temperature.
Surface Tension, Cohesion, and
Adhesion
•The energy required to increase the surface area of
a liquid, a certain amount is called surface tension.
•Generally, the stronger the intermolecular
attractions, the stronger the surface tension.
•Chemicals that break or decrease surface tension
are called surfactants.
•Cohesion is the sticking together of like molecules.
•Adhesion is the sticking of one molecule to another
surface or substance.
•Adhesion causes capillary action, or
Solids
•Solids are generally more closely packed and dense
than liquids or gases.
•Many solids are crystalline…they have a lattice of
atoms that form a strongly bound 3-D shape.
•A unit-cell is the smallest repeating pattern of a
crystal lattice.
•Some solids lack crystal structure and are
amorphous.
•Covalent compounds are not crystalline, except for
network solids, some large molecules like sugars, and
12-4 Phase Changes
Water Phase Changes
State Changes
•fusion, melting: solid to liquid phase change
•boiling, vaporization: liquid to gas phase
change
• **evaporation: liquid to gas phase change of
the particles on uncontained liquids only
•solidification, freezing: liquid to solid phase
change
•condensation: gas to liquid phase change
•sublimation: Solid to gas phase change
•deposition: gas to solid
Melting Point, Freezing Point, Boiling
Point
•When ‘point’ is added to a state-change, this
refers to the temperature at which the statechange occurs.
Vapor Pressure
•Vapor pressure is the pressure, in a sealed
container or space, caused by the vaporization
of a contained liquid.
•Vapor pressure is measured with a manometer.
Phase Changes and
Exothermic/Endothermic Nature
•Freezing, condensation, and deposition release
energy to occur….Exothermic.
•Boiling, melting, sublimation absorb energy to
occur…they are endothermic.
Phase Diagrams and Triple Point
Phase Diagram
•A phase diagram is a graphic of pressure-vtemperature that shows where solid, liquid, and
gas states exist.
•Triple-point is the location where all three
states of matter exist at one time and place.