1. Liquids and Solids
Chapter 13

2. The States of Matter

3. Liquids - Properties of Liquids:
Definite volume (density g/mL)
Fluidity
Non-compressibility
Diffusion (miscible)
Evaporation

4. Kinetic Molecular Theory description:
Lots of evidence for molecular motion (Brownian motion and diffusion)
Density is much greater than in gases molecules are closer
IM forces are more important than in gases
Strength of IM forces reflected in liquid temp. range and in vapor pressure
nonpolar covalent molecules – weakest IM and highest VP
polar covalent molecules medium range
hydrogen bonding unusually high IM and low VP
metallic liquids very high IM and very low VP
strong enough to keep fluid but weak enough to allow random particle motion
IM forces are strong enough to keep fluidity but weak enough to allow random particle motion

5. Surface Tension
Attractive force which pulls the surface molecules of a liquid together
Cohesion
Causes droplets to be spherical
Greatest ratio of volume to surface area.
Insects can walk on water.
Water has very high surface tension due to the high IM forces (H-bonding)

6. Surface tension

7. Capillary Action
Attraction of the surface of a liquid to the surface of its container.
Adhesion
Causes the meniscus in glassware.
Water stays in the bottom of a straw.
Paper towels “wick” away the water.
Mercury has an inverted meniscus.

8. Meniscus

9. Diffusion
One liquid spreads (dissolve) throughout another if they have similar molecules (polar or nonpolar)
Slower than in gases
Temperature matters
Food coloring demo in hot vs. cold water

10. Evaporation Surface event only.
Molecules on the surface with highest KE can escape the liquid phase.
Results in lower avg. KE for the liquid remaining (cooler temp)
Perspiration is a cooling event.

11. Evaporation

12. High temp.
Low temp.
% of Molecules
Kinetic Energy

13. Rate of Evaporation Increase rate by: 1. heat sample
2. increase surface area
3. blow air over the surface
Race on board alcohol vs. water vs acetone

14. Crystalline or Amorphous???
Solids
Crystalline or Amorphous???

15. SOLIDS - General Properties:
Definite shape – non-fluid
Definite volume – all surfaces are free – density (g/cm3)
Non-compressible
Very slow diffusion (if any)

16. Crystalline Solids Particles are arranged in a repeating pattern
Crystal lattice
Specific melting point
Smallest repeating unit is called the “unit cell”
Several basic types which give facets to gemstones

17. Unit Cells in the Cubic Crystal System

18. Lattice energy Energy req. to separate the crystal lattice.
This determines the strength and hardness of the crystal and the MP and BP.
Four crystal categories
Covalent network -highest MP
Ionic -high MP
Metallic -med. to high MP
Covalent molecular -lowest MP

19. Amorphous solids random arrangement of particles
MP and BP are not sharply defined
Glass, plastics, some semiconductors

20. KMT description of solids:
molecules are fixed in position
vibrational and/or rotational motion only
KE is related to temp. - as temp increases so does KE.

21. Phase Changes Change in arrangement of the particles
Requires PE changes
Temp. stays constant during a phase change. (MP or BP)
Plateau on temp./time graphs

22. Solid Gas Liquid Sublimation Melting Vaporization Freezing
Endothermic processes
Sublimation
Vaporization
Melting
Solid
Liquid
Gas
Deposition
Freezing
Condensation
Exothermic processes

23. Dynamic Equilibrium
In a closed container the vapor will develop a DYNAMIC EQUILIBRIUM.

24. Dynamic Equilibrium-
A physical state where two opposing processes occur at equal rates in the same system.
Ex. In a sealed bottle half full of water………
liquid + energy ↔ vapor
vapor ↔ liquid + energy
****must have a closed system for an equilibrium to occur.

25. Vapor Pressure (VP)
Once equilibrium occurs the vapor exerts a constant pressure on the container
VP is dependent on the temperature of the system and the type of liquid, but not the volume of the container.

26. Boiling Not the same as evaporation Occurs throughout the liquid
Rapid change of state.
VP is equal to pressure above the liquid so bubbles form and are not collapsed on the way to the surface.
Standard BP occurs at 1 atm.

28. KE and PE in phase changes
During a phase change, temperature remains constant →KE constant, PE changes
Energy is used to change arrangements of particles not speed.
During heating/cooling, temperature changes → KE changes, PE is constant

29. Heating Curve for Water
and Ice
Ice
Water and Steam
Steam
-20 20 40 60 80
100
120
220
760
800
Heating Curve for Water
KE Change
PE change
KE Change
Temp C
PE change
KE Change
Time

30. Calculating Energy (J or kJ)
Three equations
Heat = heat of fusion x mass
Heat = heat of vaporization x mass
Heat = specific heat x mass x DT

31. Energy and Phase Change
Heat of fusion: energy required to change one gram of a substance from solid to liquid.
Heat of crystallization: energy released when one gram of a substance changes from liquid to solid.
For water: 80 cal/g or 334 J/g

32. Energy and Phase Change
Heat of vaporization: energy required to change one gram of a substance from liquid to gas.
Heat of condensation: energy released when one gram of a substance changes from gas to liquid.
For water 540 cal/g or 2260 J/g

33. Phase diagrams