Liquids, Solids, and Intermolecular Forces

1. Liquids, Solids, and Intermolecular Forces Chapter 11

2. Gecko�s Hairy Feet Nanostructures on the soles of gecko feet. Thanks to about one billion hierarchically organized nanohairs, the gecko can go for a walk on walls and ceilings, unlike people. Image: Max Planck Institute for Metals Research 

4. Polar Molecules Dipole - A molecule such as HF which has a positive and a negative end. This dipolar character is often represented by an arrow pointing towards the negative charge. Dipole moments � the measure of the net molecular polarity Measure of separation of charge Measured in units of Debyes (D) = Qr (charge x separation)

6. Polar bondsNon-polar molecules

7. Intermolecular Forces Forces holding one molecule to another in a substance. van der Waals forces Dispersion forces London Forces Polar-polar interactions Hydrogen bonding

8. Figure: 11-03-08UN Title: Helium atom developing an intermolecular force Caption: Imagine a frame-by-frame movie of a helium atom in which each �frame� captures the position of the helium atom�s two electrons.Figure: 11-03-08UN Title: Helium atom developing an intermolecular force Caption: Imagine a frame-by-frame movie of a helium atom in which each �frame� captures the position of the helium atom�s two electrons.

10. Polarizability The ease with which a molecule/atoms electron cloud can be distorted, thereby inducing a dipole moment. Increasing the number of electrons increases the polarizability of an atom or molecule.

11. How does polarity affect molecular properties?

12. Figure: 11-06 Title: Boiling Points of the n-Alkanes Caption: The boiling points of the n-alkanes rise with increasing molar mass and the consequent stronger dispersion forces.Figure: 11-06 Title: Boiling Points of the n-Alkanes Caption: The boiling points of the n-alkanes rise with increasing molar mass and the consequent stronger dispersion forces.

13. Figure: 11-04-02UN Title: Pentane isomers have different dispersion forces Caption: Molar mass and molecular geometry both influence the magnitude of the dispersion force.Figure: 11-04-02UN Title: Pentane isomers have different dispersion forces Caption: Molar mass and molecular geometry both influence the magnitude of the dispersion force.

14. Figure: 11-07 Title: Dipole-Dipole Interaction Caption: Molecules with permanent dipoles, such as acetone, are attracted to one another via dipole-dipole interactions.Figure: 11-07 Title: Dipole-Dipole Interaction Caption: Molecules with permanent dipoles, such as acetone, are attracted to one another via dipole-dipole interactions.

16. Figure: 11-07-01UN Title: Formaldehyde and ethane Caption: Polar molecules have, in addition, dipole-dipole forces. This additional attractive force raises their melting and boiling points relative to nonpolar molecules of similar molar mass.Figure: 11-07-01UN Title: Formaldehyde and ethane Caption: Polar molecules have, in addition, dipole-dipole forces. This additional attractive force raises their melting and boiling points relative to nonpolar molecules of similar molar mass.

17. Figure: 11-08 Title: Dipole Moment and Boiling Point Caption: The molecules shown here all have similar molar masses but different dipole moments. The boiling points increase with increasing dipole moment.Figure: 11-08 Title: Dipole Moment and Boiling Point Caption: The molecules shown here all have similar molar masses but different dipole moments. The boiling points increase with increasing dipole moment.

18. Hydrogen Bonds A special type of polar interaction between a hydrogen atom bonded to an electronegative element and another electronegative element.

19. Figure: 11-11 Title: Hydrogen Bonding in Ethanol Caption: The H on one ethanol molecule's O-H group is attracted to the O in another ethanol's O-H group.Figure: 11-11 Title: Hydrogen Bonding in Ethanol Caption: The H on one ethanol molecule's O-H group is attracted to the O in another ethanol's O-H group.

20. Figure: 11-10-01UN Title: Comparing dipole-dipole attractions and hydrogen bonding Caption: If an O-H bond exists in a molecule, the attractions are much greater than in a molecule that has only dipole-dipole attractions. Figure: 11-10-01UN Title: Comparing dipole-dipole attractions and hydrogen bonding Caption: If an O-H bond exists in a molecule, the attractions are much greater than in a molecule that has only dipole-dipole attractions.

24. Figure: 11-14ab Title: Ion-Dipole Forces Caption: Ion-dipole forces between Na+ and the negative ends of H2O molecules and between Cl- and the positive ends of H2O molecules.Figure: 11-14ab Title: Ion-Dipole Forces Caption: Ion-dipole forces between Na+ and the negative ends of H2O molecules and between Cl- and the positive ends of H2O molecules.

25. Figure: 11-T04 Title: TABLE 11.4 Types of Intermolecular Forces Caption: The four types are presented in order of increasing strength, and includes information about their occurrence.Figure: 11-T04 Title: TABLE 11.4 Types of Intermolecular Forces Caption: The four types are presented in order of increasing strength, and includes information about their occurrence.

26. Solubility Like dissolves Like

27. Solubility Polar solvents dissolve polar molecules Nonpolar solvents dissolve nonpolar molecules Molecules with polar and nonpolar ends are frequently soluble in both polar and nonpolar solvents. Polar solvents are good for solubilizing salts.

28. Figure: 12_05-09UN Title: Solubilities of several alcohols in water Caption: As the hydrocarbon parts get larger, the solubility in water decreases.Figure: 12_05-09UN Title: Solubilities of several alcohols in water Caption: As the hydrocarbon parts get larger, the solubility in water decreases.

29. Liquids

30. Viscosity Resistance to flow If a liquid has strong intermolecular interactions then particles will not flow past each other easily and viscosity will be high.

31. Figure: 11-T05 Title: TABLE 11.5 Viscosity of Several Hydrocarbons at 20 Degrees C Caption: Viscosity depends on molecular size.Figure: 11-T05 Title: TABLE 11.5 Viscosity of Several Hydrocarbons at 20 Degrees C Caption: Viscosity depends on molecular size.

32. Figure: 11-T06 Title: TABLE 11.6 Viscosity of Liquid Water at Several Temperatures Caption: Viscosity is temperature dependent.Figure: 11-T06 Title: TABLE 11.6 Viscosity of Liquid Water at Several Temperatures Caption: Viscosity is temperature dependent.

33. Surface Tension tendency to minimize surface area

34. In Orbit (Space Shuttle), water droplets are spherical Figure: 11-20 Title: Spherical Water Droplets Caption: On the Space Shuttle in orbit, under weightless conditions, water coalesces into nearly perfect spheres held together by intermolecular forces between water molecules.Figure: 11-20 Title: Spherical Water Droplets Caption: On the Space Shuttle in orbit, under weightless conditions, water coalesces into nearly perfect spheres held together by intermolecular forces between water molecules.

35. Cohesive Forces � attraction between molecules in a liquid Adhesive Forces � attraction between liquid molecules and the surface of the tube

36. Capillary Action The ability of a liquid to flow against gravity up a narrow tube.

37. Vaporization Some Molecules in an open beaker have enough kinetic energy to vaporize from the surface of the liquid. Figure: 11-23 Title: Vaporization of Water Caption: Some molecules in an open beaker have enough kinetic energy to vaporize from the surface of the liquid.Figure: 11-23 Title: Vaporization of Water Caption: Some molecules in an open beaker have enough kinetic energy to vaporize from the surface of the liquid.

38. Figure: 11-25 Title: Vaporization in a Sealed Flask Caption: (a) When water is placed into a sealed container, water molecules begin to vaporize. (b) As water molecules build up in the gas phase, they begin to recondense into the liquid. (c) When the rate of evaporation equals the rate of condensation, dynamic equilibrium is reached. Figure: 11-25 Title: Vaporization in a Sealed Flask Caption: (a) When water is placed into a sealed container, water molecules begin to vaporize. (b) As water molecules build up in the gas phase, they begin to recondense into the liquid. (c) When the rate of evaporation equals the rate of condensation, dynamic equilibrium is reached.

39. Figure: 11-26 Title: Dynamic Equilibrium Caption: Dynamic equilibrium occurs when the rate of condensation is equal to the rate of evaporation.Figure: 11-26 Title: Dynamic Equilibrium Caption: Dynamic equilibrium occurs when the rate of condensation is equal to the rate of evaporation.

40. Vapor Pressure The pressure exerted by a vapor in equilibrium with its liquid phase.

41. Figure: 11-28 Title: Vapor Pressure of Several Liquids at Different Temperatures Caption: At higher temperatures, more molecules have enough thermal energy to escape into the gas phase, so vapor pressure increases with increasing temperature.Figure: 11-28 Title: Vapor Pressure of Several Liquids at Different Temperatures Caption: At higher temperatures, more molecules have enough thermal energy to escape into the gas phase, so vapor pressure increases with increasing temperature.

42. Figure: 11-29 Title: Boiling Caption: A liquid boils when thermal energy is high enough to cause molecules in the interior of the liquid to become gaseous, forming bubbles that rise to the surface.Figure: 11-29 Title: Boiling Caption: A liquid boils when thermal energy is high enough to cause molecules in the interior of the liquid to become gaseous, forming bubbles that rise to the surface.

45. Clausius Clapeyron Equation

46. Dry ice sublimes at �78oC and has a ?Hsub of 25.2 kJ/mol. Calculate the vapor pressure of CO2 at �100oC.

48. Calculate the boiling point of water at the summit of Pikes Peak in Colorado where the atmospheric pressure is 447.

50. Crystalline solid � atoms, ions, or molecules lie in an orderly array typically have flat well defined surfaces called faces. Amorphous solid � atoms or molecules lie in random jumble.

51. Figure: 11-50 Title: Types of Crystalline Solids Caption: Crystalline solids can be divided into three categories--molecular, ionic, and atomic--based on the individual units that compose the solid.Figure: 11-50 Title: Types of Crystalline Solids Caption: Crystalline solids can be divided into three categories--molecular, ionic, and atomic--based on the individual units that compose the solid.

52. Liquid and solid water

53. Carbon allotropes

54. Figure: 11-57 Title: Network Covalent Atomic Solids Caption: (a) In diamond, each carbon atom forms four covalent bonds to four other carbon atoms in a tetrahedral geometry. (b) In graphite, carbon atoms are arranged in sheets. Within each sheet, the atoms are covalently bonded to one another by a network of sigma and pi bonds. Neighboring sheets are held together by dispersion forces.Figure: 11-57 Title: Network Covalent Atomic Solids Caption: (a) In diamond, each carbon atom forms four covalent bonds to four other carbon atoms in a tetrahedral geometry. (b) In graphite, carbon atoms are arranged in sheets. Within each sheet, the atoms are covalently bonded to one another by a network of sigma and pi bonds. Neighboring sheets are held together by dispersion forces.

59. Phase Diagrams Graphically show conditions under which all phases are stable.

60. Phase diagram for CO2

61. Triple point A three-way intersection representing the unique temp, pressure where all three phases exist simultaneously.

62. Critical point The temperature (critical temperature) where a gas cannot be liquefied no matter what the pressure. Notice that the triple point for carbon dioxide is at 5.11 atm pressure. The liquid form doesn�t ever exist below this pressure and this is the reason that dry ice never melts but always sublimes.

63. Supercritical fluid Neither a liquid nor a gas. The liquid and gas forms become indistinguishable at this point. http://www.nottingham.ac.uk/supercritical/scintro.html

64. Phase diagram for H2O

65. Figure: 11-60-04Pr83EOC Title: Problems by Topic, 83 Caption: Consider the phase diagram shown below. Identify the phases present at points a through g.Figure: 11-60-04Pr83EOC Title: Problems by Topic, 83 Caption: Consider the phase diagram shown below. Identify the phases present at points a through g.

66. Water colorless, odorless, tasteless, liquid at ordinary temperatures only inorganic compound occurring naturally as a liquid composes ?65% of mass of living organisms excellent solvent for many things abnormally high boiling and melting point ice is less dense than water (it floats)

68. Water purification Hard water -- Contains Ca+2, Mg+2, Fe+3 and other minerals. Soft water -- Doesn�t contain Ca+2, Mg+2, Fe+3 ions. Softened water -- metal cations in hard water are replaced by Na+. Deionized water -- cations are replaced by H+ and anions are replaced by OH-