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课件网) Chapter 12 Intermolecular Forces and the Physical Properties of Liquids and Solids Intermolecular Forces and the Physical properties of Liquids and Solids 12 12.1 Intermolecular Forces Dipole-Dipole Interactions Hydrogen Bonding Dispersion Forces Ion-Dipole Interactions 12.2 Properties of Liquids Surface Tension Viscosity Vapor Pressure 12.3 Crystal Structure Unit Cells Packing Spheres Closest Packing 12.4 Types of Crystals Ionic Crystals Covalent Crystals Molecular Crystals Metallic Crystals 12.5 Amorphous Solids 12.6 Phase Changes Liquid-Vapor Phase Transition Solid-Liquid Phase Transition Solid-Vapor Phase Transition 12.7 Phase Diagrams Intermolecular Forces Intermolecular forces are attractive forces that hold particles together in the condensed phases. The magnitude (and type) of intermolecular forces is what determines whether the particles that make up a substance are a gas, liquid, or solid. 12.1 Gas Liquid Solid ATTRACTIVE FORCES electrostatic in nature Intramolecular forces bonding forces These forces exist within each molecule. They influence the chemical properties of the substance. Intermolecular forces nonbonding forces These forces exist between molecules. They influence the physical properties of the substance. * Intermolecular Forces Intermolecular forces are the attractive forces holding particles together in the condensed (liquid and solid) phases of matter Result from Coulombic attractions Dependent on the magnitude of the charge Dependent on distance between charges Weaker than forces of ionic bonding Involve partial charges Intermolecular Forces Intermolecular forces are attractive forces between molecules. Intramolecular forces hold atoms together in a molecule. Intermolecular vs Intramolecular 41 kJ to vaporize 1 mole of water (inter) 930 kJ to break all O-H bonds in 1 mole of water (intra) Generally, intermolecular forces are much weaker than intramolecular forces. “Measure” of intermolecular force boiling point melting point DHvap DHfus DHsub Types of Intermolecular Forces van der Waals forces –between atoms and molecules of pure substances Dipole-dipole interactions – attractive forces between polar molecules Hydrogen bonding – attractive force in polar molecules containing a H atom bonded to a small, highly electronegative element (N, O and F) (London) Dispersion forces – attractive forces arising from instantaneous dipoles and induced dipoles Attractive forces that act between atoms or molecules in a pure substance are collectively called van der Waals forces. Dipole-dipole interactions are attractive forces that act between polar molecules. The magnitude of the attractive forces depends on the magnitude of the dipole. Intermolecular Forces Dipole - Dipole interactions – between polar molecules Intermolecular Forces Induced dipole – induced dipole interactions- Attractive forces that arise as a result of temporary dipoles induced in atoms or mole ... ...
