2 I. Comparison of Solids, Liquids and Gases ShapeMolecularForcesDensityCompressibilityFluidityRate ofDiffusion
3 I. Comparison of Solids, Liquids and Gases ShapeIntermolecularForcesDensityCompressibilityFluidityRate ofDiffusiondefinite geometricshapesshape of containerfill the containervery strongmoderateweakmost dense(except H2O)relatively highleast denserelativelyincompressibleverycompressibleincompressiblenoneyes, it flowsyes, they flowyes, they diffuse very wellyes, but very slowlyyes, but slower than gases
5 II. Changes of State most energy gas least energy solid liquid depositionevaporationmoderate energyleast energysublimationcondensationmeltingsolidliquidfreezingQuestion: Which phase changes ADD energy, and which phase changes RELEASE energy?
6 III. Properties of Liquids A. Surface Tension - pulling together of a liquids SURFACE molecules, creating tighter arrangementB. Vapor Pressure - the gaseous pressure resulting from the vaporization of SURFACE molecules of liquidC. Boiling Point - the temperature at which a liquids vapor pressure equals the atmospheric pressureD. Viscosity – resistance to flowNote: 1) Vaporization occurs at the SURFACE of liquids2) Boiling occurs WITHIN, as well as the surface of a liquid3) Boiling Point temperatures can be raised or lowered by acorresponding change to the atmospheric pressure
7 Surface Tension pulling together of a liquids SURFACE molecules, creating tighter arrangement
10 IV. Water and It’s Properties A. Intermolecular hydrogen bonding is responsible for the high boiling point of water:OHnote: the H-bondings are additional bonds -- weaker than covalent bonds -- that must be broken before boiling can occurOHOHOH
11 B. When water freezes, the water molecules arrange themselves into hexagonal patterns: notes:1) the wider spacing between molecules causes ice to be LESS DENSE than liquid water2) water is most dense at 4 oC… warmer and colder than this causes expansion3) the volume of the hexagonal spaces in ice is equal to the volume of ice that is above the water line when floatingOHOHOHOHOH
12 C. Energy requirements for phase changes of water: 1) water requires 1 calorie (4.184 joules) to heat 1 gram of water 1 oC.2) ice requires 80 calories per gram (6.02 kJ/mol)to melt without any temperature change3) water requires 540 calories per gram (40.8 kJ/mol) to boil without any temperature changeEx: How many calories are required to melt 50 grams of ice, heat it to 100 oC, then boil it?
13 V. Phase DiagramsA. Conveniently shows the relationship between temperature, pressure and the physical state of a substance.B. Water has the only phase diagram with a negative slope to the solid/liquid boundary1) as pressure increases on ice, it liquifies2) higher pressures cause smaller volumes …3) … for water, liquid has smaller volume than solidC. Triple Point – when all 3 phases coexistD. Critical Point – 1) temp at which gas can no longer become liquid no matter what the pressure is2) pressure required to produce liquefaction at the critical temperature