1. Review:
1. Which of the substances has the highest normal bp?
2. Would a 50oC sample of ethanol boil under an external pressure of 50 kPa?
3. Based on the vapor pressure curves provided, which substance would have the strongest IMF’s?

2. Goals for the next 3 days:
Draw simple representations of different types of solids that illustrate important aspects of their structure
Analyze models of different solid types in order to explain the properties of these substances.

3. So what is a solid?
Cool any gas down enough that when they collide, they do not bounce off elastically

4. So what is a solid?
Cool any gas down enough that when they collide, they do not bounce off elastically
Continue to cool the sample …

5. So what is a solid?
Cool any gas down enough that when they collide, they do not bounce off elastically
Continue to cool the sample …
Ordered and organized array of closely packed particles …

6. So what is a solid?
Ordered and organized array of closely packed particles.
Particles have vibrational motion.
Most solids have a repeatable crystal structure called a lattice
Since particles are close-packed, solids are incompressible

7. What types of substances form solids?
Room temperature gases or liquids (weaker IM force substances) will solidify when cooled (KE is removed until IM forces take hold)
Room temperature solids are substances that have very strong intermolecular OR intramolecular attractions.

8. Phase Change Energy Factors:
heat +
S  L (melting)
S  G (subliming)
Endothermic
heat +
L  S + heat (freezing)
G  S + heat (depositing)
Exothermic

9. Chemistry of Solids
Types of Solids

10. Chemistry of Solids
Types of Solids

11. Molecular Solids
Composed of:
Molecules attracted to one another via intermolecular forces

13. Molecular Solids
Composed of:
Molecules attracted to one another via intermolecular forces
If the molecules are polar the attractive force will be …
If the molecules are non-polar the attractive force will be …

14. Molecular Solids
Composed of:
Molecules attracted to one another via intermolecular forces
Melting points:
Generally lower MP’s than other solids
Stronger IM forces will result in higher melting points

15. Molecular Solids
Electrical conduction:
A substance can conduct electricity only if it has free-flowing charged particles
Molecular solids are not expected to conduct electricity in any state (solid, molten, dissolved)

16. Molecular Solids
What about the molecular structure of solid water vs. solid methane explains the higher melting point of water? Why does neither solid conduct electricity?