Transcript 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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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.
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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 tension; attraction of the surface of a liquid to the surface of a solid.
Ex: water transport from roots to leaves
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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.
SOLIDS
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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.
Properties of Solids
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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.
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High Density and Incompressibility Low diffusion rate: very slow
Crystalline Solids
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Crystal structure = 3D arrangement of particles of crystals.
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a) 7 types of crystals- pg. 369 Unit Cell = smallest portion of a crystal that shows the 3D structure.
Binding Forces in Crystals
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Ionic Crystals: NaCl Strong electrostatic forces holds it together.
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Hard, brittle, high melting pts.
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.
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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.
Amorphous Solids
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No regular pattern of atoms.
Large range of melting points.
Examples: glass, plastics
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
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
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
Vapor Pressures of varying substances at different temps.
Boiling
The conversion of a liquid atmospheric pressure. vapor within the ENTIRE liquid. Occurs when the vapor pressure in the bubble =
Phase Diagram for Water
Shows the conditions under which the phases of a substance can exist.
Triple Point: Indicates the temp and pressure at which the solid, liquid, gas coexist.
Critical Point: indicates the critical temp. and pressure of a substance 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)