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To learn about dipole-dipole, hydrogen bonding and London dispersion forces

Objectives 14.1 Intermolecular Forces and Phase Changes. To learn about dipole-dipole, hydrogen bonding and London dispersion forces To understand the effect of intermolecular forces on the properties of liquids To learn some of the important features of water

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To learn about dipole-dipole, hydrogen bonding and London dispersion forces

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  1. Objectives 14.1 Intermolecular Forces and Phase Changes • To learn about dipole-dipole, hydrogen bonding and London dispersion forces • To understand the effect of intermolecular forces on the properties of liquids • To learn some of the important features of water • To learn about interactions among water molecules • To understand and use heat of fusion and heat of vaporization

  2. A. Intermolecular Forces Matter can be described by its physical properties. The physical properties of a substance generally depend on the spacing between particles (atoms, molecules, ions) that make up the substance and the forces of attraction among them.

  3. A. Intermolecular Forces Forces of attraction between particles (including the noble gases and also different parts of some large molecules) are important in determining many macroscopic properties of a substance, including how the observable physical state changes with temperature.

  4. A. Intermolecular Forces • Reviewing what we know • Low density • Highly compressible • Fill container • Gases • Solids • High density • Slightly compressible • Rigid (keeps its shape)

  5. A. Intermolecular Forces • Intermolecular forces – occur between molecules • Intramolecular forces – occur inside the molecules

  6. A. Intermolecular Forces • Dipole – dipole attraction

  7. A. Intermolecular Forces • Hydrogen Bonding • Occurs between H and highly electronegative atom (for example N, O, F)

  8. A. Intermolecular Forces • Hydrogen Bonding • Affects physical properties • Boiling point

  9. A. Intermolecular Forces • London Dispersion Forces • Formation of instantaneous dipoles

  10. A. Intermolecular Forces • London Dispersion Forces • Nonpolar molecules

  11. A. Intermolecular Forces • London Dispersion Forces • Become stronger as the sizes of atoms or molecules increase

  12. B. Water and Its Phase Changes • Heating/cooling curve

  13. B. Water and Its Phase Changes • Normal boiling point – at 1 atm = 100oC • Normal freezing point – at 1 atm = 0oC • Density • Liquid water = 1.00 g/mL • Ice = 0.917 g/mL

  14. C. Energy Requirements for the Changes of State • Changes of state are physical changes • No chemical bonds are broken

  15. C. Energy Requirements for the Changes of State • Molar heat of fusion – energy required to melt 1 mol of a substance • Molar heat of vaporization – energy required to change 1 mol of a liquid to its vapor

  16. Objectives 14.2 Vapor Pressure and Boiling Point • To understand the relationship among vaporization, condensation and vapor pressure • To relate the boiling point of water to its vapor pressure

  17. A. Evaporation and Vapor Pressure • Vaporization or evaporation • Endothermic

  18. A. Evaporation and Vapor Pressure • Vapor Pressure • Amount of liquid first decreases then becomes constant • Condensation - process by which vapor molecules convert to a liquid • When no further change is visible the opposing processes balance each other - equilibrium

  19. A. Evaporation and Vapor Pressure • Vapor Pressure • Vapor pressure - pressure of the vapor present at equilibrium with its liquid • Vapor pressures vary widely - relates to intermolecular forces

  20. B. Boiling Point and Vapor Pressure

  21. B. Boiling Point and Vapor Pressure

  22. Objectives 14.3 Properties of Solids • To learn about the types of crystalline solids • To understand the interparticle forces in crystalline solids • To learn how the bonding in metals determines metallic properties

  23. Solids The type of bonding in the solid state can be deduced from the properties of the solid state.

  24. A. The Solid State: Types of Solids • Crystalline solids

  25. A. The Solid State: Types of Solids

  26. A. The Solid State: Types of Solids

  27. B. Bonding in Solids

  28. B. Bonding in Solids • Ionic Solids • Stable substances with high melting points • Held together by strong forces between ions

  29. B. Bonding in Solids • Molecular Solids • Fundamental particle is a molecule • Melt at relatively low temperatures • Held together by weak intermolecular forces

  30. B. Bonding in Solids • Atomic Solids • Fundamental particle is the atom • Properties vary greatly • Group 8 - low melting points • Diamond - very high melting point

  31. B. Bonding in Solids • Bonding in Metals • Metals are held together by nondirectional covalent bonds (called the electron sea model) among the closely packed atoms

  32. B. Bonding in Solids • Bonding in Metals • Metals form alloys of two types • Substitutional – different atoms are substituted for the host metal atoms

  33. B. Bonding in Solids • Bonding in Metals • Metals form alloys of two types • Interstitial – small atoms are introduced into the “holes” in the metallic structure

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