1. Liquids and Solutions
Ch. 14 and 15

2. Unit Outline Water (14.1-14.2) Intermolecular forces (14.3)
Difference in phases
Requirements for phase changes
Intermolecular forces (14.3)
Evaporation and Vapor Pressure (14.4)
Solutions ( )

3. Water (or any other substance)
Constant, random motion
No interaction with other water
particles
Rigid, Strong
Interactions
With the other
particles
Particles move freely,
But still interact with the
Other particles

4. How do you change phases?
Heating/cooling curve

5. Changing Phases Temperature is constant during a phase change.
What changes between molecules as a substance goes through a phase change?
Is the substance itself changing?
Interactions between neighboring molecules?

6. Review Chemical Bonding
Ionic
Covalent
Polar Covalent
A chemical bond is an intramolecular force
Intramolecular force: force that holds a molecule together.

7. Intermolecular forces
Intermolecular force: Force between two molecules, keeping the molecules close to each other

8. So…
In order for a solid to be converted to a liquid, energy must be added to the substance to loosen the intermolecular forces between the particles.
In order for a liquid to be converted to a gas, energy must be added to the substance to overcome or break the intermolecular forces between the particles.

9. Types of Intermolecular Forces
Dipole-Dipole attraction
Remember Polarity?
Molecules with dipole moments orient themselves so that the positive end of one molecule is close to the negative end of another molecule

11. Hydrogen Bonding
Unusually strong dipole-dipole interaction involving hydrogen atoms.
Made possible by the small size of the H atom

12. London Dispersion
London Dispersion: Weak intermolecular force that holds non-polar atoms/molecules together.

13. You Know You Have… Dipole-Dipole attraction when the molecule is polar
Hydrogen Bonding when the molecule has an H bonded to a N, O, or F.
London Dispersion when the atom or molecule is nonpolar.

14. Identify the Intermolecular Force
NH3
CH3OH
(CH3)3N I2 He
CCl4
CH4 HF
HCl
NO2
H-Bonding
Dipole-Dipole
London Dispersion