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Slide 1Intermolecular forces are responsible for the differentphases of matter [gas, liquid, solid] –• gases have only weak interactions between molecules,• liquids and solids have strong interactions.States of Matter
Slide 2States of MatterThe fundamental difference between states of matter isthe distance between particles.
Slide 3States of MatterBecause in the solid and liquid states particles are closertogether, we refer to them as condensed phases.
Slide 4The States of Matter• The state a substance is in at aparticular temperature andpressure depends on opposingfactors:The kinetic energy of theparticlesThe strength of the attractionsbetween the particles
Slide 5Hydrogen Bonding• The dipole-dipole interactions experiencedwhen H is bonded to N, O, or F are unusuallystrong.• We call these interactions hydrogen bonds.
Slide 6Hydrogen BondingHydrogen Bond:Molecules in which H is bound to the very electronegativeO, N, or F.
Slide 7Hydrogen BondingCH4 110 KSiH4 160 KGeH4 175 KSnH4 215 KH2O 373 KH2S 215 KH2Se 225 KH2Te 270 KEffect of Hydrogen Bonding on Boiling Point:Effect of Hydrogen Bonding on Boiling Point:
Slide 8Hydrogen Bonding• The nonpolar series (SnH4to CH4) follow theexpected trend.• The polar series followsthe trend from H2Tethrough H2S, but water isquite an anomaly.
Slide 9Intermolecular ForcesApplication of HydrogenApplication of HydrogenBonding!!Bonding!!Cellulose molecules arepresent in the trunk of thetree. They form stronghydrogen bonds between Oand H.
Slide 12Phase Changes• Molar Heat of Fusion (∆Hfus):The energy required to melt one mole of solid (kJ).• Molar Heat of Vaporization (∆Hvap):The energy (kJ) required to vaporize one mole of liquid.• Molar Heat of Sublimation (∆Hsub):The energy (kJ) required to sublime one mole of solid.∆Hsub=∆ Hfus + ∆Hvap
Slide 14GasesWhich elements exist normally as gases?
Slide 15GasesGases are –• compressible• expandable• form homogeneous mixturesWe can use a model in which –• molecules move rapidly• respond quickly to changes in volume• the volume of the molecules is very small (0.1%)compared with the total volume occupied by a gas
Slide 16Gases and PressureThe pressure of the atmosphere …
Slide 17Gases and PressureThe units of pressure that you need to know:* atmosphere (atm)* Pa (N/m2, 101,325 Pa = 1 atm)* Torr (760 Torr = 1 atm)* bar (1.01325 bar = 1 atm)* mm Hg (760 mm Hg = 1 atm)* [lb/in2(14.696 lb/in2= 1 atm)]
Slide 18The Ideal Gas LawStarting with the Ideal Gas Law we can work back to aseries of extremely important relationships that describethe behaviour of a gas under different conditions –• Boyle’s Law• Charles’ Law• Avogadro’s Principle …
Slide 19Boyle’s Law• Pressure–Volume Law (Boyle’s Law):The volume of a fixedamount of gas maintainedat constant temperature isinversely proportional to thegas pressure –P1V1 = P2V2Pressure1Volume ∝
Slide 20Charles’ LawTemperature–Volume Law (Charles’ Law):V ∝ TThe volume of a fixedamount of gas at constantpressure is directlyproportional to the Kelvintemperature of the gas –V1 = V2T1 T2
Slide 21Avogadro’s PrincipleThe Volume–Amount Law (Avogadro’s Principle):V ∝ nAt constant pressure andtemperature, the volume ofa gas is directlyproportional to the numberof moles of gas present –V1 = V2n1 n2
Slide 22The Ideal Gas Law• Ideal gases obey the following equation -• The gas constant R = 0.08206 L·atm·K–1·mol–1or …. = 8.31451 J.K-1.mol-1TRnVP ⋅⋅=⋅when pressureis in Pascals
Slide 23Ideal GasesStandard Temperature and Pressure (STP):“1 mole of an ideal gas occupies 22.414 L at STP”STP conditions are –273.15 K (0 oC) and 1 atm pressure
Slide 24Ideal GasesThe molar volumes of real gases do differ from 22.41 L …but not by that much -
Slide 25Vapor Pressure• At any temperature, some molecules in a liquid haveenough energy to escape.• As the temperature rises, the fraction of molecules thathave enough energy to escape increases.
Slide 26Vapor PressureAs more moleculesescape the liquid, thepressure they exertincreases.
Slide 27Vapor PressureThe liquid and vaporreach a state of dynamicequilibrium: liquidmolecules evaporate andvapor moleculescondense at the samerate.
Slide 28Vapor Pressure• The boiling point of a liquidis the temperature atwhich its vapor pressureequals atmosphericpressure.• The normal boiling point isthe temperature at whichits vapor pressure is 760torr.
Slide 29Gas StoichiometryProblem:Carbonate bearing rocks (like limestone, CaCO3) react withdilute acids such as HCl to produce carbon dioxide -CaCO3(s) + 2 HCl(aq) CaCl2(aq) + CO2(g) + H2O(l)How many grams of CO2 are produced from completereaction of 33.7 g of limestone? What is the volume of theCO2 at RTP?
Slide 30Gas StoichiometryProblem:Assuming no change in temperature and pressure, calculatethe volume of O2 (in liters) required for the completecombustion of 14.9 dm3of butane (C4H10):2 C4H10(g) + 13 O2(g) → 8 CO2(g) + 10 H2O(l)
Slide 31Gas StoichiometryProblem:Hydrogen gas, H2, can be prepared by allowing zinc metal toreact with aqueous HCl. How many dm3of H2 can beprepared at 742 mm Hg and 15oC if 25.5 g of zinc (Mr =65.4 g/mol) is allowed to react?Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2(aq)
Slide 35Sodium chloride … “rock salt”• Na+ions are the smaller spheres (102 pm) that sit in the “holes” betweenthe larger Cl-ions (181 pm)• the Cl-ions form a “loose” cubic structure• counting up the number of Na+ions and Cl-ions in the unit cellgives us 4 of each (ions on a corner count for 1/8 ; ions on a face for ½ ;ions on an edge for ¼ ; and the ion in the center for 1)• other examples of the rock salt structure are KBr, RbI, MgO, CaO, and AgCl
Slide 36SolidsCrystalline—particles arein a highly orderedarrangement.Silicon dioxide
Slide 37Covalent-Network andMolecular Solids• Diamonds are an example of a covalent-network solid inwhich atoms are covalently bonded to each other.They tend to be hard and have high melting points.
Slide 38Covalent-Network andMolecular Solids• Graphite is an example of a molecular solid in whichatoms are held together with van der Waals forces.They tend to be softer and have lower melting points.
Slide 39Metallic Solids• Metals are not covalentlybonded, but the attractionsbetween atoms are too strongto be van der Waals forces.• In metals, valence electronsare delocalized throughout thesolid.