1. Chapter 13 IMF, Solids and Liquids

2. Kinetic Molecular Theory
Matter is composed of particles in constant motion.
The speed of the particles depends on temperature. (remember: temp is related to KE) They are directly related.
Particles that make up a gas are so small that their volume can be ignored.

3. Kinetic Molecular Theory
4. The individual particles of a gas do not attract or repel one another.
5. When gas particles collide with one another (or the walls of the container) they bounce rather than stick. These collisions are elastic.

4. Intermolecular forces
The forces that condense matter.

5. Forces of attraction
Intramolecular forces-the force inside compounds holding them together (Ionic and covalent bonds)
Covalent Bond

6. Forces of attraction
Intermolecular forces- the force between or among particles that hold them together

7. Intermolecular Forces
If all particles of matter at the same temperature have the same kinetic energy, why are they in different phases of matter?
The answer lies in what is holding the particles together.

8. Types of Intermolecular Forces
1. Dispersion Forces or London Dispersion forces:
weakest intermolecular forces.
between nonpolar molecules
Instantaneous dipole moment caused by uneven distribution of electrons on one side of the atom.
Temporary
Exist between all molecules
Polarizability- the ease with which an electron cloud becomes charged increases with MM. In other words, LD forces increase with MM.
Examples: CH4 is a gas while C25H52 is a solid

9. Types of Intermolecular Forces
2.Dipole-dipole forces:
Attraction between polar molecules to maximize (+) (-) and minimize (-) (-).
Contain permanent dipoles
Stronger than London dispersion forces if comparing molecules with the same mass
1% as strong as ionic bonds

10. Types of Intermolecular Forces
3. Hydrogen Bonding:
A specific type of dipole-dipole
Occurs between a molecule containing Hydrogen and another molecule containing either fluorine, oxygen or nitrogen.
Examples: H2O, NH3, HF

11. Hydrogen Bonds and Boiling Points
Small size of molecules plus hydrogen bonds cause H2O, HF and NH3 to have relatively high boiling points.

12. Hydrogen Bonding and Water
Hydrogen bonds explain why water:
is a liquid at room temperature, even though it is very light.
has a high boiling point
surface tension
Forms crystals when frozen
The solid is less dense than the liquid

13. Intermolecular Forces and States of Matter
The stronger the forces between the particles,
(a) the higher the melting point.
(b) the higher the boiling point.
(c) the lower the vapor pressure (partial pressure of vapor in equilibrium with liquid or solid in a closed container at a fixed temperature).
(d) the higher the viscosity (resistance to flow).
(e) the greater the surface tension (resistance to an increase in surface area).

14. Liquids Contain particles that flow Takes the shape of container
Fluidity- has the ability to flow. Both Gases and Liquids are classified as fluids
Takes the shape of container
Has a definite volume
Denser than gases

15. Liquids Viscosity - Measure of the resistance of a liquid to flow.
Increases with intermolecular forces”
Increases with molecular size.
Decreases with temperature

16. Liquids
Surface tension - The resistance to an increase in its surface area
High surface tension indicates strong IMF’s.
Molecules are attracted to each OTHER. A molecule in the interior of a liquid is attracted by the molecules surrounding it, whereas a molecule at the surface of a liquid is attracted only by the molecules below it and on each side.

17. Capillary Action Cohesive forces- between polar molecules
Adhesive forces- between polar molecule and a polar molecule of a container (SiO2 in glass)
Cohesive greater than adhesive in H2O
Adhesive forces greater than cohesive in Hg