1. Phase Changes and Intermolecular Forces
Chapter

2. 1. Properties of solids, liquids, and gases
Solids: densely packed and organized
Gases: widely spaced and disorganized
Liquids: in between, disorganized, but still fairly dense.

3. 2. What states of water can coexist at 0 C
2. What states of water can coexist at 0 C? What are these temperatures known as?
0 C
Solid/Liquid
Melting/Freezing
100 C
Liquid/Gas
Boiling

4. 3. Draw the Heating Curve of Water

5. 3. the Heating Curve of Other Substances
Iron 
Nitrogen:
Melting/Freezing Point: -210 C
Boiling Point: -195 C

6. 4. Does the figure look like sections from the Water and Methanol lab?

7. 5. Does it take more heat to increase the temperature of water from 0C to 100C or to evaporate it completely?
It takes more energy to go though a phase change than it does to change the temperature. Look a the amount of time/energy it took to change the liquid to a gas (which is boiling).

8. 6. What is the difference between intermolecular forces and Intramolecular forces?
Intermolecular = between multiple molecules/atoms
Examples: London Dispersion, Hydrogen bonds, Ionic Bonding, dipole-dipole forces
Intramolecular = Within a molecule
Example: Covalent, Polar covalent, and Ionic Bonding

9. 7. Define Heat of fusion and Heat of Vaporization.
Heat of Fusion: The amount of energy it takes to turn a substance from a solid to a liquid. (Takes place at MP)
Heat of Vaporization: The amount of energy it take to turn a substance from a liquid to a gas. (Takes place at BP)

10. 7. Which is usually a higher amount of energy
7. Which is usually a higher amount of energy? Does this make sense given the properties of S, L, and G?
The heat of vaporization is much higher that the heat of fusion.
IMFA = Intermolecular Forces of Attraction
In solids the IMFA are holding the molecules in a neat organized crystal lattice. When it melts (Heat of fusion) the IMFA still hold the molecules together, but they are disorganized. When a substance is boiled (heat of vaporization) the IMFA are broken and the molecules bounce around the container. It takes more energy to break the IMFA than it does to disorganize it.

11. 8. Rank the IMFA in order of increasing strength:
London Dispersion forces
Dipole-Dipole forces
Hydrogen Bonds
Ionic Bonding

12. Draw flow chart while we discuss the different types

13. 8. Rank the IMFA in order of increasing strength:
1. London Dispersion forces
Type of Intramolecular force: Covalent Bonding or Non-Bonded Noble Gas
Polarity: Non-polar
Cause of IMFA:
Electrons are not always equally spaced around a non-polar molecule. Causes temporary dipoles.

14. 8. Rank the IMFA in order of increasing strength:
1. Dipole-Dipole forces
Type of Intramolecular force: Polar Covalent Bonding
Polarity: Polar (but not Hydrogen bonds)
Cause of IMFA:
The dipole moments in polar molecules cause the molecule to have positive and negative ends. The positive end of molecules attract the negative ends of other molecules.

15. 8. Rank the IMFA in order of increasing strength:
3. Hydrogen Bonds
Type of Intramolecular force: Polar Covalent Bonding (But only when H is bonded to O, F, and N)
Polarity: More polar than dipole-dipole forces
Cause of IMFA:
Similar to dipole-dipole, but hydrogen bonds are more polar, so there is a greater attraction between molecules

16. 8. Rank the IMFA in order of increasing strength:
4. Ionic Bonding
Type of Intramolecular force: Ionic Bonding
Polarity: Very Polar, full charges
Cause of IMFA:
The positive cations are strongly attracted to the negative anions that surround it (and vice- versa).

17. 9. Which elements does hydrogen need to be bonded with in order to have hydrogen bonding?

18. 10. Which IMFA does each molecule use?
Molecules
Type of IMFA
Phase at Room Temp
HBr
Gas BP= -66
NF3
Gas BP= -129 Kr
Gas BP= -153 N2
Gas BP= -195
H2S
Gas BP= -60
NaCl
Solid BP= 1413
H2O
Liquid BP= 100

19. 11. Rank the IMFA in increasing BP
London Dispersion forces
Dipole-Dipole forces
Hydrogen Bonds
Ionic Bonding

20. 10. Which IMFA does each molecule use?
Molecules
Type of IMFA
Phase at Room Temp
HBr
 Dipole-Dipole
Gas BP= -66
NF3
Gas BP= -129 Kr
 London Dispersion
Gas BP= -153 N2
Gas BP= -195
H2S
 Hydrogen
Gas BP= -60
NaCl
 Ionic
Solid BP= 1413
H2O
Hydrogen
Liquid BP= 100

21. 12. Which atoms/molecules have the greatest London Dispersion forces?
The larger the size of the atoms the bigger the instantaneous dipole and the stronger the force. The Higher the BP

22. Which would have a higher BP? (remember BP is correlated to polarity)
Kr or Xe
N2 or O2
NF3 or NH3
CH4 or CH3OH
NH3 or H2O