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Exploring Changes in Phases: Solids, Liquids, and Gases

This chapter delves into the transitions between phases driven by temperature and pressure variations, intermolecular forces, vaporization, vapor pressure, and phase diagrams. It covers dispersion, dipole-dipole, hydrogen bonding, and ion-dipole forces. Learn about the Clausius-Clapeyron equation, boiling point, critical temperature, and phase diagrams, all illustrated through practical examples and theoretical foundations.

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Exploring Changes in Phases: Solids, Liquids, and Gases

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  1. Chapter 11 CHM 108 Suroviec Spring 2014

  2. I. Solids, Liquids and Gasses

  3. A. Changes between phases • Using temperature, pressure or both you can convert from one phase to another

  4. II. Intermolecular Forces • Originate from interactions between charges, partial charges and temporary charges

  5. A. Dispersion Forces • One intermolecular force present in all molecules and atoms s the dispersion force

  6. A. Dispersion Forces • Magnitude of dispersion force depends on how easily the atom/molecule can polarize

  7. B. Dipole – Dipole Forces • Exists in all molecules that are polar – that have permanent dipoles.

  8. B. Dipole – Dipole Forces • Polarity is important in determining miscibility

  9. C. H – Bonding • hydrogen bond = a special dipole-dipole interaction between they hydrogen atom in a polar N-H, O-H, or F-H bond and an electronegative O, N, or F atom.

  10. D. Ion – Dipole Forces • Occurs when an ionic compound is mixed with a polar compound

  11. IV. Vaporization and Vapor Pressure • Phase is a homogeneous part of the system in contact with other parts of the system but separated from them by a well – defined boundary.

  12. A. Vapor Pressure • Equilibrium is reached between liquid and vapor, the net number of molecules exchanging does not change.

  13. Clausius-Clapeyron Equation ln P = - Vapor Pressure Versus Temperature DHvap + C RT B. Vapor Pressure and Temperature Molar heat of vaporization (DHvap) is the energy required to vaporize 1 mole of a liquid at its boiling point.

  14. Example • Glacier National Park in Montana is a great vacation spot. It is about 4100 ft above sea level with an atmospheric pressure of 681 mm Hg. At what temperature does water (DHvap = 40.7 kJ/mol) boil in the park?

  15. C. Boiling Point • The boiling point is the temperature at which the (equilibrium) vapor pressure of a liquid is equal to the external pressure. • The normal boiling point is the temperature at which a liquid boils when the external pressure is 1 atm.

  16. D. Critical Temperature and Pressure • There are temperatures and pressures for gasses and liquids that when reached the molecule exhibit unique properties • The critical temperature (Tc) is the temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure. • The critical pressure (Pc) is the minimum pressure that must be applied to bring about liquefaction at the critical temperature.

  17. V. Phase Diagrams • The melting point of a solid or the freezing point of a liquid is the temperature at which the solid and liquid phases coexist in equilibrium. • The sublimation of a solid or the deposition of a gas is the temperature at which the solid and gas phases coexist in equilibrium. • The vaporization of a liquid or the condensation of a gas is the temperature at which the solid and gas phases coexist in equilibrium.

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