Gen Chem 2, week 1 notes
Gen Chem 2, week 1 notes 603613
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This 3 page Class Notes was uploaded by Emmanuel Notetaker on Sunday January 17, 2016. The Class Notes belongs to 603613 at University of Cincinnati taught by waddell, D in Winter 2016. Since its upload, it has received 74 views. For similar materials see Gen Chem II in Chemistry at University of Cincinnati.
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Date Created: 01/17/16
Chap 12Intermolecular forces: Liquids, Solids and Phase Changes Intermolecular forces Forces of attraction between molecules, weaker than covalent and ionic bonds There are four types of intermolecular forces (Weakest to Strongest) 1. London Dispersion Forces (LDF) Present in all substances, but exclusive in non –polar substances. LDF’s increase in molecular weight or molecular size. 2. DipoleDipole Forces: Present in all polar molecules. DipoleDipole forces increase with increased polarity 3. Hydrogen Bonding: Present in molecules that contain NH, OH or FH bond. Hydrogen bonding is far stronger than either DipoleDipole or LDF. Strength: FH > OH > NH. 4. Ionic Bonds: Extremely high melting and boiling points due to the High electrostatic attraction between molecules. The more electrons that are share b/n atoms or the more polarized the bond is, the stronger the intermolecular forces are. Crystalline solids Atoms, ions or molecules arranged in an orderly, repeating, 3 dimensional pattern called a crystal lattice can be ionic (exSalt) or covalent (exSugar) Amorphous solids lack an ordered internal structure, the atoms are randomly arranged ex: glass, rubber, plastic Hygroscopic compounds Hydrated salts with a low vapor pressure that remove moisture from the air. ex sugar, iodine, sulphric acid Deliquescent compounds Compounds that remove enough water from the air to dissolve completely and form solutions Allotropes Two or more different molecular forms of the same element in the same physical state Vaporization conversion of liquid to gas or vapor, kinetic energy must be Condensation conversion of gas to a liquid Sublimation The transition of a substance directly from solid to gas phase without passing through liquid phase Evaporation conversion of liquid to gas at the surface of a liquid that is not boiling Chap 12Intermolecular forces: Liquids, Solids and Phase Changes happens faster when heated cooling process Why is evaporation a cooling process? The particles with the highest kinetic energy escape first and take the heat with them, the particles left have a lower average kinetic energy so that the liquid's temperature decreases How is vapor pressure created When particles of a liquid evaporate in a closed container, the particles collide with the walls and produce vapor pressure What is vapor pressure The force due to the gas above the liquid in a closed space Relationship between temperature and vapor pressure If there is higher temperature, kinetic energy increases which means more collisions When the vapor pressure is equal to atmospheric pressure, the substance will boil. Volatile liquid that evaporates easily due to weak IMFs between molecules (nonvolatile liquids evaporate slowly because of their strong IMFs). Boiling point Temperature at which the vapor pressure of a liquid is just equal to the external pressure (boiling point changes as external pressure changes) low pressure, boiling points lower b/c particles need less kinetic energy to escape liquids high pressure, boiling point is higher b/c more kinetic energy is needed to escape liquid What does the atmosphere do in addition to the IMFs present between molecules? it exerts a downward force viscosity High resistance to flow against gravity ex> honey, molasses Miscibility: The dissolving point for polar and nonpolar bonds Chap 12Intermolecular forces: Liquids, Solids and Phase Changes What creates surface tension in water Water is a polar molecule and can't form hydrogen bonds with air and turns into the body of the liquid
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