Chapter 12 Intermolecular Forces and the Physical Properties of Liquids and Solids

Chapter 12 Intermolecular Forces and the Physical Properties of Liquids and Solids

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Chapter 12 Intermolecular Forces and the Physical Properties of Liquids and Solids Intermolecular forces: the attractive forces that hold particles together in the condensed phases Magnitude of forces determines whether the particles that make up a substance are a gas liquid or solid Van der waals forces: attractive forces that act between atoms or molecules in a pure substance Dipole-dipole interactions are attractive forces that act between polar molecules The partial positive charge on one molecule is attracted to the partial negative charge on a neighboring molecule In general the larger the dipole the larger the attractive force Substances held together by larger intermolecular attractions will require more energy to separate the particles and will therefore boil at higher temps Hydrogen bonding: is a special type of dipole-dipole interaction. Occurs inly in molecules that contain H bonded to a small highly electronegative atom such as N, O, or F and results in a very strong dipole-dipole attraction Ex. In HF the F atom draws electron density away from H very effectively, leaving H basically unshielded and with a very large partial positive charge. The large partial charge is strongly attracted to the large partial negative charge (lone pairs) of F on a neighboring HF molecule Dispersion Forces: attractive forces that act between all molecules , including nonpolar molecules, resulting from the formation of instantaneous dipoles and induced dipoles Arise from the movement of electrons in nonpolar molecules
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This note was uploaded on 01/26/2012 for the course CHEM 307 taught by Professor Several during the Fall '08 term at Rutgers.

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Chapter 12 Intermolecular Forces and the Physical Properties of Liquids and Solids

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