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LIQUIDS AND SOLIDS

LIQUIDS AND SOLIDS. 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? Fluid : a substance that flows and hence takes the shape of its container. Properties of Liquids.

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LIQUIDS AND SOLIDS

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  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? • Fluid: a substance that flows and hence takes the shape of its container.

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

  4. Surface Tension: a force that pulls adjacent parts of a liquid’s surface, thereby decreasing surface area. Ex: bug “walking” on water. C apillary 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. 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.

  6. SOLIDS • 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 • Definite shape and volume • Melting point: • Crystalline Solids: Definite melting point, KE of particles overcome attractive forces of solid. • Amorphous Solids: No definite melting point, Supercooled liquids. • High Density and Incompressibility • Low diffusion rate: very slow

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

  9. Binding Forces in Crystals • Ionic Crystals: • NaCl • Strong electrostatic forces holds it together. • Hard, brittle, high melting pts. • Covalent Molecular Crystals: • Nonpolar: H2, CH4 vs. Polar: H20, NH3 • Covalently bonded molecules held together by intermolecular forces. • Low melting points, soft, easily vaporized.

  10. 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 • Metallic Crystals: • Metal atoms surrounded by sea of valence electrons. • High electrical conductivity, Melting Points vary.

  11. Amorphous Solids • No regular pattern of atoms. • Large range of melting points. • 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.) Equilibrium Equations: 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) 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 vapor pressure in the bubble = atmospheric pressure.

  17. Phase Diagram for Water Triple Point: Indicates the temp and pressure at which the solid, liquid, gas coexist. Shows the conditions under which the phases of a substance can exist. 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 Point: indicates the critical temp. and pressure of a substance

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