1. Liquids and Solids
“CONDENSED STATES OF MATTER”

2. Intra- vs. Inter- intramolecular forces inside molecules
hold atoms together into molecule
intermolecular forces
between molecules
get weaker as phase changes from
S – L – G
Generally, intermolecular forces are much weaker than intramolecular forces.

3. Orientation of Polar Molecules in a Solid
Dipole-Dipole Forces
Attractive forces between polar molecules
Orientation of Polar Molecules in a Solid

4. happens between H and N, O, or F
Hydrogen Bonding
happens between H and N, O, or F
very strong type of dipole-dipole attraction
because bond is so polar
because atoms are so small

5. Hydrogen Bonding
Bonding between hydrogen and more electronegative neighboring atoms such as oxygen and nitrogen
Hydrogen bonding between ammonia and water

6. London Dispersion Forces
The temporary separations of charge that lead to the London force attractions are what attract one nonpolar molecule to its neighbors.
increase with the size of the molecules.
in every molecular compound
only important for nonpolar molecules and noble gas atoms
weak, short-lived
caused by formation of temporary
dipole moments
Fritz London

7. London Dispersion Forces

8. Relative Magnitudes of Forces
The types of bonding forces vary in their strength as measured by average bond energy.
Strongest
Weakest
Covalent bonds (400 kcal/mol)
(intramolecular)
Hydrogen bonding (12-16 kcal/mol )
(intermolecular)
Dipole-dipole interactions (2-0.5 kcal/mol)
(intermolecular)
London forces (less than 1 kcal/mol)
(intermolecular)

9. London Forces in Hydrocarbons
Dispersion forces usually increase with molar mass.

10. Boiling point as a measure of intermolecular attractive forces

11. Practice which has highest boiling pt?
HF, HCl, or HBr?
Identify the most important intermolecular forces :
BaSO4
H2S Xe
C2H6 P4
H2O
CsI HF
ionic
dipole-dipole
London Dispersion
London Dispersion
London Dispersion
H-bonding
ionic

12. Which has stronger IMF’s?
CO2 or OCS
CO2: nonpolar so only LD
OCS: polar so dipole-dipole
PF3 or PF5
PF3: polar so dipole-dipole
PF5: nonpolar so only LD
SF2 or SF6
SF2: polar so dipole-dipole
SF6: nonpolar so only LD
SO3 or SO2
SO3: nonpolar so LD only
SO2: polar so dipole-dipole ? ? ? ?

13. DO WE GET IT? To be collected!
Please begin the following problems. You may
work cooperatively on this assignment.
Problems: pg. 475 #12, 20, 30, 32, 34 and
36 (a,b and d only!)
To be collected!

14. Some Properties of a Liquid
Surface Tension: The resistance to an increase in its surface area (polar molecules, liquid metals).
Strong intermolecular forces
High surface tension =

15. EMOO BUG
Surface of water behaving
like it had an “elastic skin”

16. attracted to each other
Capillary Action: Spontaneous rising of a liquid in a narrow tube.
Cohesion is the intermolecular attraction between like molecules
Adhesion
Cohesion
Adhesion is an attraction between unlike molecules
attracted to glass
attracted to each other

17. Properties of a Liquid Viscosity: Resistance to flow
High viscosity is an indication of strong intermolecular forces

18. Which of the following consistently have the highest melting points?
Metals
Salts
Molecular crystals
Alkanes
Hydrogen-bonded compounds.
Answer: B

19. How sharp are you? Gases can be compressed more easily than liquids
because:
Gas molecules are smaller than liquid molecules
B. The kinetic energy of gas molecules is higher than that
found in liquids
The average intermolecular distances are greater in gases
than those found in liquids.
Intermolecular forces increase as gas moleculues are brought
closer together.
E. None of the above.
Answer: C In a gas, the molecules are separated by a large distance
and are able to be compressed by increasing the pressure. They move
independently of one another because there is no appreciable intermolecular
interactions among them.

20. In which of the following are the intermolecular
forces listed from the weakest to the strongest?
Dipole-dipole>London>hydrogen bonds
London<dipole-dipole<hydrogen bonds
Hydrogen bonds<dipole-dipole<London
London>hydrogen bonds>dipole-dipole
London>Javier bonds>dipole-dipole>Ali forces
Answer: B

21. Which of the following compounds will NOT hydrogen- bond>?
CF4
CH3OH
H2NCH2CH2CH3
HOCH2CH2OH
HClO
Answer: A

22. Water has a higher capillary action than mercury due to:
Higher dipole-dipole forces between the water molecules
Strong cohesive forces within water.
Very significant induced intermolecular attractions.
Weak adhesive forces in water
Strong cohesive forces in water which work with strong
adhesive forces.
Answer: E. The strong adhesive forces leads to a creeping effect
as water moves up the narrow tubing and the strong cohesive forces
attempt to minimize the surface area.

23. Small drops of water tend to bead up because of:
High capillary action
the shape of the meniscus
The resistance to increased surface area.
Low London dispersion forces
Weak covalent bonds.
Answer: C. This is a description of surface tension, which is a
result of high dipole-dipole forces between water molecules. These
intermolecular forces are also called…..hydrogen bonds!

24. Several liquids are compared by adding them to a series
of 50 mL graduated cylinders, then dropping a steel
ball of uniform size and mass into each. The time
required for the ball to reach the bottom of the cylinder
is noted. This is a method used to compare the
differences in a property of liquids known as:
Surface tension
Buoyancy
Capillary action
Viscosity
Surface contraction
Answer: D. The resistance to flow of any fluid is called viscosity. As
You would predict, liquids with high viscosity (ex: maple syrup) have
large intermolecular forces.

25. General Classification of Solids
Crystalline Solids: Well-ordered, definite arrangement of atoms. (Examples- metals, H2O, diamond)
Amorphous: No pattern to the arrangement of particles. (Examples- glass, plastic, wax)

26. Representation of Components in a Crystalline Solid
Lattice: A 3-dimensional system of points designating the centers of components (atoms, ions, or molecules) that make up the substance.

27. Types of Crystalline Solids
There are four types of crystalline solid:
- Molecular (formed from atoms or molecules) - usually soft with low melting points and poor conductivity.
- Covalent network (formed from atoms) - very hard with very high melting points and poor conductivity.
- Ionic (formed form ions) - hard, brittle, high melting points and poor conductivity.
- Metallic (formed from metal atoms) - soft or hard, high melting points, good conductivity, malleable and ductile.

28. Bonding in Crystalline Solids
Know these!!
Metallic bonds are formed from metal nuclei floating in a sea of electrons.

29. Crystalline Solids
Molecular
Covalent Network
Ionic
Metallic

30. Metal Alloys
Substitutional Alloy: some metal atoms replaced by others of similar size.
brass = Cu/Zn

31. Metal Alloys (continued)
Interstitial Alloy: Interstices (holes) in closest packed metal structure are occupied by small atoms.
steel = iron + carbon

32. Phase Changes & Energy
Endothermic: melting, evaporating/boiling & sublimation
Exothermic: freezing, condensation, & deposition

33. Phase Changes & Energy
heat of vaporization: the heat energy required to evaporate a given mass of liquid at a constant temperature
heat of fusion: the heat energy required to melt a given mass of solid at a constant temperature
The temperature, (average KE), during a phase change (such as boiling) does not change!
Any heat added during boiling gives more molecules enough energy to escape the liquid.
Heating Curve

34. Phase Changes & Energy
Generally, it will take more heat to vaporize a liquid than to melt a solid… (∆H(vap) > ∆H(fusion) ) Why?
Every intermolecular bond is broken when vaporizing, but only some of the intermolecular forces break when melting solids. ?

35. Practice Time: Please attempt the following problems
(at your workstations!):
pg : 72, and 88.

36. Gases can be liquefied by: increasing pressure at some temperature.
Liquefying Gases
Gases can be liquefied by:
increasing pressure at some temperature.
decreasing the temperature at some pressure.
- Critical temperature: the highest temperature at which a substance can remain a liquid regardless of the pressure applied.
- Critical pressure: the pressure needed at the critical temperature.

37. Phase Diagrams
Shows the relationship between the 3 phases of matter at various temperatures and pressures.
Triple Point: All 3 phases of matter at equilibrium.
Critical Point: The highest temperature at which the liquid phase can exist.

38. Phase Diagrams of H2O and CO2
Notice the slope of the solid–liquid equilibrium line.

39. Practice Time:
Please attempt the following problems. You may scatter and work with anyone you please.
pg. 480: #91.