2. The behavior of gases in motion is described by the kinetic molecular theory. Kinetic molecular theory:  gases are small particles, separated by empty space, with no significant volume or forces acting among the particles (Free to move)  particles are in constant, random, straight-line motion; collisions between the particles are elastic (no KE is lost) the energy of the particles can be explained in terms of the equation KE= ½ mv 2 Have same KE(kinetic energy) at a given temp

3. FORCES OF ATTRACTION Intramolecular forces – attractive forces that hold atoms together in ionic, covalent, and metallic bonds (chemical bonds) Intermolecular forces – attractive forces among or between particles; weaker than intramolecular forces - include London dispersion forces, dipole-dipole forces, and hydrogen bonds= van der waals

4. Mark each as ionic or covalent, then circle all that are polar and underline all that are nonpolar 1.RaI 2 2.CH 4 3.NH 3 4.O 2 5.LiF 6.N 2 7.AlI 3

5. Hydrogen bonds – special type of dipole- dipole attraction between molecules containing a hydrogen bonded to a small highly electronegative atom with at least one lone electron pair - F-NO fluorine, nitrogen and oxygen are all small, electronegative atoms that when bonded to hydrogen within a molecule form hydrogen bonds with the hydrogen of another molecule important in the behavior of molecules, especially water Examples: HF, NH 3, H 2 O

6. Dipole-dipole forces – attractions between oppositely charged regions of polar molecules; stronger than London dispersion forces Examples: HCl, H 2 S, HCN

7. London dispersion forces – weak force resulting from temporary shifts in the density of electrons in electron clouds (a temporary dipole) between 2 nonpolar molecules - among the halogens (all diatomic) the varying strength of the dispersion forces resulting from the electron cloud explains why fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid

8. - viscosity –measure of the resistance of a liquid to flow; determined by the IM forces, shape of the particles, and temperature - surface tension – measure of the inward pull by particles on the interior of a liquid that results from a net attractive force pulling down due to a lack of molecules above those on the surface - surfactants are substances that decrease the surface tension of water, such as detergents and soaps -

9. capillary action – phenomenon that results when the adhesive forces between molecules of a liquid and a container are greater than the cohesive forces between the molecules of the liquid; causes the water to rise along the inner walls of the container; if the container is narrow enough, the liquid is drawn upward in a movement called capillary action DIAPERS Can hold 200 times mass in fluid!

10. - wetting agent – the difference between the adhesive and cohesive forces is also a measure of how well a substance acts as a “wetting” agent; if the cohesive forces are less than the adhesive forces, the substance is not a good wetting agent, if the adhesive forces are greater than the cohesive forces the substance is a better wetting agent

14. NEXT

19. Energy is used to overcome the Intermolecular forces in order to phase change. (or Strengthen IM forces on cooling curve ) Temp does not change during a phase change.

20. Exothermic Phase Changes Vs. Endothermic Phase changes Freezing – liquid to a solid; amt of energy can be calculated using the heat of fusion; occurs at the melting point, which varies with the IM forces Condensation – gas to a liquid; amt of energy can be calculated using the heat of vaporization; occurs at the boiling point, which varies with the IM forces Deposition – gas to a solid Melting – solid to a liquid; amt of energy can be calculated using the heat of fusion; melting point, which varies with the types of IM forces involved Vaporization – which is a phase change from a liquid to a gas (Evaporate) at the surface of the substance at a temperature BELOW the boiling point Sublimation – solid to a gas

21. Vaporization – liquid to a gas throughout the substance; amt of energy can be calculated using the heat of vaporization occurs at the boiling point, which varies with the IM forces; NOT the same as evaporation evaporation in a closed container creates vapor pressure on the surface of the liquid - an increase in temperature increases the rate of evaporation

22. Properties of solids: - density – higher than that of a liquid of the same substance at the same temperature due to difference in IM forces (exception – WATER; water is actually densest at 4 C; water at 0 C floats so warmer water is actually at the bottom; important in ecological systems because the colder on top acting as an “insulator” and preventing lakes and ponds of any depth from freezing solid) - crystalline – solids whose atoms, ions or molecules are arranged in an orderly, geometric, 3-D structure, forming a framework called a crystal lattice; there are seven major categories of crystal lattices, each based on the shape of the unit cell (see p. 401) (atomic, molecular, covalent network, ionic, and metallic) (see Table p. 402 and explanation pp. 402-3) Amorphous solids – one in which the particles are not arranged in a regular, repeating pattern; tend to “flow”; ex) glass, rubber, plastic