Unit 6 – Solids, Liquids And Solutions

Unit 6 – Solids, Liquids and Solutions13.2 The Nature of LiquidsI.A Model for LiquidsA. Liquids are Fluids1. Substances that can flow and therefore take the shape of their containerB. Liquids have Relatively High Density1. 10% less dense than solids (average)a. Water is an exception2. 1000x more dense than gasesC. Liquids are Relatively Incompressible1. The volume of liquids doesn't change appreciably when pressure is appliedD. Liquids have the Ability to Diffuse1. Liquids diffuse and mix with other liquids2. Rate of diffusion increases with temperature ( average Kinetic Energy)E. Evaporation and Boiling1. Evaporationa. Molecules with sufficient kinetic energy escape as vapor from the surface of the liquid2. Vapor Pressurea. A measure of the force exerted by a vapor above its liquid3. Boilinga. The change of a liquid to bubbles of vapor that appear throughout the liquidb. The normal boiling point is the temperature at which a substance boils at 101.3 kPac. The boiling point of a substance decreases as the atmospheric pressure decreasesF. Formation of Solids1. Freezing (or Solidification)a. The physical change of a liquid to a solid by removal of heatSolidLiquidGas13.3 The Nature of SolidsI.A Model for SolidsA. Types of Solids1. Crystalline Solids - substances in which the particles are arranged in an orderly, geometric, repeatingpattern2. Amorphous Solids - substances in which the particles are arranged randomlyB. Definite Shape and VolumeC. Definite Melting Point1. Melting is the physical change of a solid to a liquid by the addition of heat2. Melting point is the temperature at which a solid becomes a liquida. Crystalline solids have definite melting pointsb. Amorphous solids do not have definite melting pointsD. High Density and IncompressibilityE. Low Rate of Diffusion1. Two solids in contact will experience VERY SLOW rates of diffusion1

II.Crystalline SolidsA. Crystal Structure1. The total three dimensional arrangement of particles of a crystalB. Unit Cell1. The smallest portion of a crystal lattice that shows the three-dimensional pattern of the entire latticeIII.Amorphous SolidsA. "Amorphous"1. Greek for "without shape"B. Formation of amorphous solids1. Rapid cooling of molten materials can prevent the formation of crystalsa. Glassb. Obsidian13.4 Changes of StateI.Boiling and CondensationA. Boiling1. The conversion of a liquid to a vapor within the liquid as well as at its surface. It occurs when theequilibrium vapor pressure of the liquid equals the atmospheric pressureB. Boiling Point1. The temperature at which the equilibrium vapor pressure of the liquid equals the atmosphericpressurea. Water boils at 100 C at 1 atm pressureb. Water boils above 100 C at higher pressuresc. Water boils below 100 C at lower pressuresC. Condensation1. The conversion of a gas to a liquid by the removal of energyII.Freezing and MeltingA. Freezing Point1. The temperature at which the solid and liquid are in equilibrium at 1 atm2

2. For pure crystalline solids, the melting point and freezing point are the same3. Temperature remains constant during a phase changeB. Sublimation and Deposition1. Sublimation is the change of state from a solid directly to a gasa. Dry ice Æ Gaseous CO22. Deposition is the change of state from a gas directly to a solidIII.Phase DiagramsA. Phase Diagram1. A graph of pressure versus temperature that shows the conditions under which the phases of asubstance exist (notice that pressure is on a logarithmic scale)B. Triple Point1. The temperature andpressure conditions atwhich the solid,liquid, and vapor ofthe substance cancoexist at equilibriumC. Critical Temperature1. The temperature atabove which thesubstance cannotexist in the liquidstate, regardless ofpressurea. For water,the criticaltemperatureis 373.99 CD. Critical Pressure1. The lowest pressureat which the substance can exist as a liquid at the critical temperaturea. For water, the critical pressure is 217.75 atmE. Critical Point1. The point on the graph describing simultaneously the critical temperature and the critical pressureP 217.75 atmTemperature 373.99 C15.1 Water and Its PropertiesI.Liquid WaterA. Surface Tension1. Surface Tensiona. A force that tends to pull adjacent parts of a liquid's surface together, thereby decreasingsurface area to the smallest possible sizeb. Hydrogen bonding in water creates stronger than normal surface tension2. Capillary Actiona. The attraction of the surface of a liquid to the surface of a solidB. Vapor Pressure1. Water has a very low vapor pressure due to the strong hydrogen bonding on the surfaceII.Water in the Solid StateA. Density1. Water is one of only a few substances that is less dense as a solid than as a liquidB. High melting point1. No other substance with such small molar mass has so high freezing/melting point3

III.Summary of Water’s Important PropertiesBond TypeBond angleNormal Boiling pointNormal Melting PointPolar105 100 0 CDensity of ice (0 C)Density of water (0 C)Point of maximum densityMolar heat of fusionMolar heat of vaporization0.917 g/cm30.999 g/cm33.98 C6.009 kJ/mole40.79 kJ/mole15.2 Homogeneous Aqueous SystemsI.SolutionsA. Soluble1. Capable of being dissolvedB. Solution1. A homogeneous mixture of two or more substances in a single phaseC. Solvent1. The dissolving medium in a solutionD. Solute1. The dissolved substance in a solutionE. Types of solutions1. Gaseous mixturesa. Air is a solution2. Solid solutionsa. Metal alloys3. Liquid solutionsa. Liquid dissolved in a liquid (alcohol in water)b. Solid dissolved in a liquid (salt water)II.Solutes: Electrolytes vs. NonelectrolytesA. Electrolyte1. A substance that dissolves in water to give a solution that conducts electric current2. Solutions of acids, bases and salts are electrolytesB. Nonelectrolyte1. A substance that dissolves in water to give a solution that does not conduct an electric currentC. Measuring Conductivity1.2.3.Good conductorsa. Lamp glows brightly, ammeter registers a substantial currentModerate conductorsa. Lamp is dull, ammeter registers a small currentNonconductorsa. Lamp does not glow, ammeter may not register a current at all4

15.3 Heterogeneous Aqueous SystemsI.SuspensionsA. A mixture from which particles settle out upon standingII.ColloidsA. Colloidal Dispersions (Colloids)1. Tiny particles suspended in some medium2. Particles range in size from 1 to 1000 nm.B. Tyndall Effect1. Scattering of light by particlesa. Light passes through a solutionb. Light is scattered in a colloidExamplesFog, aerosol spraysSmoke, airborne bacteriaWhipped cream, soap sudsMilk, mayonnaisePaint, clays, gelatinMarshmallow, polystyrene foamButter, cheeseRuby glassTypes of olidLiquidSolidSolidColloid TypeAerosolAerosolFoamEmulsionSolSolid foamSolid emulsionSolid sol16.1 Properties of SolutionsI.Factors Affecting the Rate of DissolutionA. Increasing the Surface Area of the Solute (Particle size)1. Finely divided substances dissolve more rapidlyB. Agitating a Solution1. Stirring or shaking brings solvent into contact with more solute particles2. Added energy temporarily increases solubilityC. Heating1. Heating always increasing the rate of dissolution of solids in liquidsII.SolubilityA. Solution Equilibrium1. The physical state in which the opposing processes of dissolution and crystallization of a solute occurat equal ratesB. Saturation Levels1. Saturated solutiona. A solution that contains the maximum amount of dissolved solute2. Unsaturated solutionsa. A solution that contains less solute than a saturated solution under the existing conditions3. Supersaturated Solutionsa. A solution that contains more dissolved solute than a saturated solution contains under thesame conditionsC. Solubility Values1. The solubility of a substance is the amount o int Constant for Water1. The freezing-point depression of the solvent in a 1-molal solution of a nonvolatile, nonelectrolytesolute2. Kf -1.86 C/mB. Freezing-Point Depression1. The difference between the freezing points of the pure solvent and a solution of a nonelectrolyte inthat solvent t f K f mC. Molal Boiling-Point Constant for Water1. The boiling point elevation of the solvent in a 1-molal solution of a nonvolatile, nonelectrolyte solute2. Kb 0.51 C/mD. Boiling-Point Elevation1. The difference between the boiling points of the pure solvent and a solution of a nonelectrolyte inthat solvent t b K b m7

19.1 Acid-Base TheoriesI.AcidsA. Properties of Acids1. Aqueous solutions have a sour taste2. Acids change the color of acid-base indicators3. Acids react with carbonates to produce water, a salt, and carbon dioxideNa2CO3(s) 2HCl Æ 2NaCl H2O CO24. Some acids react with active metals to release hydrogenZn(s) H2SO4(aq) Æ ZnSO4(aq) H2(g)5. Acids react with bases to produce salts and waterHCl(aq) NaOH(aq) Æ NaCl(aq) H2O(l)6. Acids conduct electric currentB. Strength of Acids1. Strong acids ionize completely in solution2. Weak acids ionize only slightly and are weak electrolytesStrong acidsH2SO4HClO4HClHNO3HBrHIWeak acidsH3PO4HFHC2H3O2H2CO3H2SHCNC. Organic Acids1. Covalent molecular substances containing a carboxyl groupa. (-COOH)2. Weak acids (only slightly ionize)3. Examplesa. Butyric acid - in rancid butterb. Lactic acid - in sour milkc. Citric acid - in citrus fruitd. Acetic acid - in vinegarII.BasesA. Properties of Bases1. Aqueous solutions of bases have a bitter taste2. Bases change the color of acid-base indicators3. Dilute aqueous solutions of bases feel slippery4. Bases react with acids to produce salts and water5. Bases conduct electric currentB. Aqueous Solutions of Bases1. Ionic bases dissociate to some extent when placed in water2ONaOH ( s ) H Na (aq) OH (aq)2.3.Basic solutions are referred to as "alkaline"Molecular bases produce hydroxide ions through a reaction with waterNH 3 ( g ) H 2 O(l ) NH 4 (aq ) OH (aq)C. Strength of Bases1. Strength of ionic bases is linked to solubilitya. High solubility strong baseb. Low solubility weak base2. Molecular bases tend to be weak regardless of solubility8

III.Arrhenius Acids and BaseesA. Acids1. Acids are hydrogen-containing compounds that ionize in solution to produce H ionsB. Basees1. Bases are compounds that produce OH- ions in solutionIV.Bronsted-Lowry Acids and BasesA. Acids1. Acids are proton (H ion) donors in solutionB. Basees1. Bases are proton acceptors in solution9

13.2 The Nature of Liquids I. A Model for Liquids A. Liquids are Fluids 1. Substances that can flow and therefore take the shape of their container B. Liquids have Relatively High Density 1. 10% less dense than solids (average) a. Water is an exception 2. 1000x more dense than gases C. Liquids are Relatively Incompressible 1.