1. LIQUIDS AND SOLIDS

2. LIQUIDS: Why are they the least common state of matter? 1. Liquids and K.M.T.  Are particles in constant motion? Spacing? Kinetic Energy? Attractive forces? Kinetic Energy? Attractive forces?  Fluid: a substance that flows and hence takes the shape of its container.

3. Properties of Liquids 1. High Density: 1000x greater than gases, 10% less dense than solids. 2. Relatively Incompressible: Water’s volume only decreases 4% under 1000atm of pressure! 3. Can diffuse: Slower in liquids than gases due to: Slower in liquids than gases due to: slower motion and attractive forces.

4. 4. Surface Tension: a force that pulls adjacent parts of a liquid’s surface, thereby decreasing surface area. Ex: bug “walking” on water. Capillary Action: related to surface Capillary Action: related to surface tension; attraction of the surface of a liquid to the surface of a solid. Ex: water transport from roots to leaves

5. 5. Vaporization: Process by which liquid  gas. Evaporation: Process by which particles escape from the surface of a nonboiling liquid. Boiling: change of a liquid to vapor bubbles appearing throughout the liquid. Boiling: change of a liquid to vapor bubbles appearing throughout the liquid.

6. SOLIDS 1. Solids and K.M.T.  More closely packed than liquids or gases.  Intermolecular forces are VERY effective.  Only vibrational movement.  Crystalline vs. Amorphous (glass) solids.

7. Properties of Solids 1. Definite shape and volume 2. Melting point:  Crystalline Solids: Definite melting point, KE of particles overcome attractive forces of solid.  Amorphous Solids: No definite melting point, Supercooled liquids. 3. High Density and Incompressibility 4. Low diffusion rate: very slow

8. Crystalline Solids 1. Crystal structure = 3D arrangement of particles of crystals. a)7 types of crystals- pg. 369 2. Unit Cell = smallest portion of a crystal that shows the 3D structure.

9. Binding Forces in Crystals 1. Ionic Crystals:  NaCl  Strong electrostatic forces holds it together.  Hard, brittle, high melting pts. 2. Covalent Molecular Crystals:  Nonpolar: H 2, CH 4 vs. Polar: H 2 0, NH 3  Covalently bonded molecules held together by intermolecular forces.  Low melting points, soft, easily vaporized.

10. 3. Covalent Network Crystals:  Diamond (C) X, Silicon Carbide (SiC) X  Giant molecules that extend indefinitely- each atom is covalently bonded to neighboring atom.  Hard, Brittle, High Melting Points 4. Metallic Crystals:  Metal atoms surrounded by sea of valence electrons.  High electrical conductivity, Melting Points vary.

11. Amorphous Solids 1. No regular pattern of atoms. 2. Large range of melting points. 3. Examples: glass, plastics

12. Equilibrium Equilibrium = a dynamic condition in which 2 opposing changes occur at equal rates in a closed system. Equilibrium and State Changes: ex: Evaporation of water in a closed container (assuming constant temp.) (assuming constant temp.) Equilibrium Equations: liquid + heat energy vapor liquid + heat energy vapor

13. Le Chatelier’s Principle When a stress is applied to a system at equilibrium, the system will respond in a way to minimize that stress. (Stress= change in temp, pressure, concentration) When a stress is applied to a system at equilibrium, the system will respond in a way to minimize that stress. (Stress= change in temp, pressure, concentration) ex: liquid + heat vapor ex: liquid + heat vapor

14. Equilibrium Vapor Pressure of a Liquid  The pressure exerted by a vapor in equilibrium with its liquid at a given temp.  Increases as temp. increases (How can we explain this using KMT?)  Volatile vs. Nonvolatile Liquids:  Volatile liquids have WEAK forces of attraction, therefore they evaporate readily. Ex: ethanol

15. Vapor Pressures of varying substances at different temps.

16. Boiling The conversion of a liquid  vapor within the ENTIRE liquid. Occurs when the The conversion of a liquid  vapor within the ENTIRE liquid. Occurs when the vapor pressure in the bubble = atmospheric pressure. vapor pressure in the bubble = atmospheric pressure.

17. Phase Diagram for Water Critical Temperature = Substance can’t exist as a liquid above this temperature (only as a gas). Critical Temperature = Substance can’t exist as a liquid above this temperature (only as a gas). Critical Pressure = Lowest pressure at which the substance can exist as a liquid at the critical temperature. (any lower P, it’s a gas) Critical Pressure = Lowest pressure at which the substance can exist as a liquid at the critical temperature. (any lower P, it’s a gas) Shows the conditions under which the phases of a substance can exist. Critical Point: indicates the critical temp. and pressure of a substance Triple Point: Indicates the temp and pressure at which the solid, liquid, gas coexist.