1. Properties of Solids

2. Ionic Crystals Held together by electrostatic attraction
General properties: Hard, brittle, high MP, poor conductors of heat and electricity, form electrolytic solutions.
Examples: NaF, LiCl, CaCO3
Usually a metal bonded with a nonmetal. Why?

3. Molecular Crystals
Held together by LD forces, dipole-dipole forces, or hydrogen bonds.
General properties: Soft, low melting point, poor conductors of heat and electricity.
Example: SO2

4. Covalent Network Crystals
Held together by covalent bonds in extensive 3D network
No discrete molecules are present
General properties: Hard, high melting points, poor conductors of heat and electricity
Examples: Diamond (C), Quartz (SiO2)

5. Metallic Crystals Held together by metallic bonds (sea of electrons)
General properties: vary in degrees of hardness and melting points, good conductors of heat and electricity (why?)
Examples: all metallic elements
Strength of representative metals determined by number of valence electrons
Ex. Na mp = 97.6 oC while Al mp = 660oC

6. Amorphous Solids Crystalline—consist of crystals
Crystal—particles are arranged in a orderly, geometric, repeating pattern.
Amorphous—particles are arranged randomly.
No definite melting point, flows over a range of temperatures.

7. Phase Changes

8. Liquid-Vapor Equilibrium
Particles in a liquid possess enough KE to escape from the surface.
Vaporization
Gaseous molecules exert a vapor pressure.
Dynamic equilibrium between condensation and vaporization
Vapor pressure measured at this point is called equilibrium vapor pressure

9. Liquid-Vapor Equilibrium
Vapor pressure—dependent on temperature
Molecules with higher kinetic energy have a higher vapor pressure
Molar heat of vaporization (∆Hvap) = energy required to vaporize on e mole of a liquid.
Dependent on strength of IMFs
Inverse relationship with vapor pressure
High IMFs = low vapor pressure, high ∆Hvap.

10. Liquid-Vapor Equilibrium
Boiling point—Temperature at which the vapor pressure is equal to the external pressure
Bubbles form within the liquid instead of escaping from the surface
Pressures exerted on liquid = atmospheric
Pressure inside bubbles is due to vapor pressure of liquid
Bubble rises to the surface when vapor pressure of liquid overcomes atmospheric pressure

11. Liquid-Vapor Equilibrium

12. Liquid-Solid Equilibrium
Melting point—the temperature at which solid and liquid phases coexist in equilibrium.
Molar heat of fusion (∆Hfus) = the energy required to melt 1 mole of a solid.
∆Hfus determined by strength of IMFs or bond strengths.
Methane = 0.83 kJ/mol
Ethanol = 7.61 kJ/mol
Mercury = 23.4 kJ/mol

13. Solid-Vapor Equilibrium
Sublimation = Solid to vapor
Deposition = Vapor to solid
Molar heat of sublimation = energy required to sublime 1 mole of a substance.
Sum of molar heats of fusion and vaporization if change is at constant temperature.

14. Heating Curves

15. Phase Diagrams
Phase diagram—graph in which pressure versus temperature is used to show the conditions of phase changes for a specific substance.
Triple Point—point at which all three states of matter coexist.
Critical point—point of critical temp and critical pressure.
Critical temp—temperature above which the substance cannot exist as a liquid
Critical pressure—lowest pressure that substance can exist as a liquid.