1. Liquids and Solids

2. Characteristics of Liquids and Solids
What properties allow you to classify a substance as a solid, liquid, or gas?

3. Property Solid Liquid Gas
Volume
Shape
Relative density
Compressibility
Fluid?
Space between particles
Diffusion rate
Motion of particles
(amount and type)
Forces between particles?

4. Surface Tension
Surface tension is the tendency for liquid surface to contract.
Depends on IMFs
Compounds that interfere with the IMFs and reduce surface tension are called surfactants.

5. The molecular basis of surface tension.
Figure 12.18
The molecular basis of surface tension.
the net vector
for attractive
forces is downward
hydrogen bonding
occurs across the surface
and below the surface
hydrogen bonding
occurs in three
dimensions

6. stronger cohesive forces
Figure 12.19
Shape of water or mercury meniscus in glass.
capillarity
stronger cohesive forces
adhesive forces
H2O Hg

7. Liquid-gas equilibrium.
Figure 12.4
Liquid-gas equilibrium.

8. Vapor pressure as a function of temperature and intermolecular forces.
Vapor pressure = the pressure of the vapor resulting from evaporation of a liquid (or solid) above a sample of the liquid (or solid) in a closed container
What factors affect the vapor
pressure?
Figure 12.6
Vapor pressure as a function of temperature and intermolecular forces.

9. Boiling Point
Temperature at which the vapor pressure of the liquid = atmospheric pressure
Normal boiling point
vpliquid = 760 mmHg
condensing point = boiling point

10. What if…?
You are camping at a high altitude of 10,000 ft where the atmospheric pressure is 535 mmHg. If you boil an egg for 10 minutes will it be hard-boiled just right, overdone, or runny? Explain your choice.

11. Subliming Point
Temperature at which the vapor pressure of the solid equals atmospheric pressure
Depositing point = subliming point
Iodine subliming

12. Dipole moment and boiling point.
Figure 12.12
Dipole moment and boiling point.

13. Hydrogen bonding and boiling point.
Figure 12.13
Hydrogen bonding and boiling point.

14. Molecular shape and boiling point.
Figure 12.16
Molecular shape and boiling point.
fewer points for dispersion forces to act
more points for dispersion forces to act

15. Freezing Point
Temperature at which liquid and solid are in equilibrium
Not affected by pressure but does depend on IMFs and molar mass
Melting point = freezing point

16. The hexagonal structure of ice.
Figure 12.21
The hexagonal structure of ice.

17. The striking beauty of crystalline solids.
Figure 12.22
The striking beauty of crystalline solids.

18. The crystal lattice and the unit cell.
Figure 12.23
The crystal lattice and the unit cell.
lattice point
unit cell
portion of a 3-D lattice
portion of a 2-D lattice
unit cell

19. Diffraction of x-rays by crystal planes.
Figure 12.27
Diffraction of x-rays by crystal planes.

20. Table 12.5 Characteristics of the Major Types of Crystalline Solids
Interparticle Forces
Physical Behavior
Particles
Examples (mp,0C)
Atomic
Atoms
Dispersion
Soft, very low mp, poor thermal & electrical conductors
Group 8A(18)
[Ne-249 to Rn-71]
Molecular
Molecules
Dispersion, dipole-dipole, H bonds
Fairly soft, low to moderate mp, poor thermal & electrical conductors
Nonpolar - O2[-219], C4H10[-138], Cl2
[-101], C6H14[-95]
Polar - SO2[-73], CHCl3[-64], HNO3[-42], H2O[0.0]
Ionic
Positive & negative ions
Ion-ion
attraction
Hard & brittle, high mp, good thermal & electrical conductors when molten
NaCl [801]
CaF2 [1423]
MgO [2852]
Metallic
Atoms
Metallic bond
Soft to hard, low to very high mp, excellent thermal and electrical conductors, malleable and ductile
Na [97.8]
Zn [420]
Fe [1535]
Network
Atoms
Covalent bond
Very hard, very high mp, usually poor thermal and electrical conductors