Chapter11notes part1

Chapter11notes part1 - 1 Intermolecular Forces / Liquids...

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Unformatted text preview: 1 Intermolecular Forces / Liquids and Solids I. Kinetic Molecular Theory (KMT) of Liquids and Solids KMT of gases has been discussed. This is based on no appreciable forces between molecules mostly empty space very compressible KMT of liquids and solids is based on very little empty space little to no compressibility Sometimes, liquids and solids are referred to as condensed states of matter. A phase is a homogeneous part of a system in contact with other parts of the system but separated from the other parts by a well-defined boundary. Water is an example of a substance where all three phases are commonly observed. 2. Gas/Liquid/Solid Comparisons Phase Volume/Shape Intermolecular Force Strength Density Ability to be compressed Molecular Motion Gas Assumes volume and shape of its container Low to none Low Very high Very free Liquid Definite volume / assumes shape of its container High High Slight Molecules slide past one another freely Solid Definite volume and shape High High Almost none Very little only vibration about fixed positions Sealed container containing water gas (water vapor) solid (ice) liquid 2 II. Intermolecular Forces Intermolecular forces are forces that act between molecules. Intramolecular forces are forces that act between atoms in the same molecule. These are the forces that hold molecules together bonds. In general, inter molecular forces are weaker than intra molecular forces. A. Types of intermolecular forces Note: Although called intermolecular forces, some of these include ion/molecule forces. 1. Dipole-dipole forces act between molecules possessing a permanent dipole moment. e.g., HCl Solid: maximum alignment Liquid: less rigid Gas: virtually no alignment In general, stronger dipole-dipole interactions lead to higher melting points. Note: Dipole-dipole forces act between all molecules with permanent dipole moments. 2. Ion-dipole forces act between ions and molecules possessing a permanent dipole moment. + + cation anion These forces account for the solubility of ionic compounds. e.g., NaCl( s ) --> Na + ( aq ) + Cl ( aq ) Hydration is an example of ion- dipole forces. H O H Na + Cl H O H H O H H O H H O H H O H H O H H O H H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl H Cl + + + + + + + + + 2 II. Intermolecular Forces Intermolecular forces are forces that act between molecules. Intramolecular forces are forces that act between atoms in the same molecule. These are the forces that hold molecules together bonds. In general, inter molecular forces are weaker than intra molecular forces. A. Types of intermolecular forces Note: Although called intermolecular forces, some of these include ion/molecule forces....
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This note was uploaded on 04/16/2008 for the course CHEM 1303 taught by Professor Maguire during the Fall '08 term at SMU.

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Chapter11notes part1 - 1 Intermolecular Forces / Liquids...

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