Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
SolidsandLiquidsBoilingPoint(BP)andMeltingPoint(MP)Giventhesubstances’MPandBP,predictwhatphaseitisinatroomtemperature.Whenwewalkintothelab,whatwillwesee?Asolid,liquidorgas?Animportantquestiontoanswerfirstis:Whatisroomtemperature(Troom)indegreesCelsius(°C)?
Substance MP(°C) BP(°C) PhaseatTroom
Mercury ‐39 357 LiquidBecauseMP<TroomandBP>Troom
Methane ‐187 ‐161 GasBecauseMP<TroomandBP<Troom
Aluminum 660 2519 SolidBecauseMP>TroomandBP>Troom
Hexane ‐95 69 LiquidBecauseMP<TroomandBP>Troom
MacroscopicandMolecularViewsofSubstancesDescribethefollowingsubstancesfromthemacroscopicandmolecularviewsusingwordsandsketches.Youmayneedtolookonlineforthemolecularstructureofsubstancessuchasnaphthalene,ethylacetate,andformaldehyde.Wedonotexpectyoutoknowthesestructures.SolidDiamond(Carbon)CovalentSolidbecause:non‐metals,MPhigh
Macroscopic:Transparent,sparklingsolid.Extremelyhard.Highmeltingpoint.Microscopic:Onlycarbonatomsheldtogetherinarigid,tetrahedralpattern.
Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
SolidTableSalt(NaCl)Ionicsolidbecause:metal&non‐metal,MPhigh
Macroscopic:Whitecrystal.Highmeltingpoint.Dissolveseasilyinwater.Tastessalty.Microscopic:Latticeofalternatingsmallcations(Na+)andlargeanions(Cl‐)heldtogether bycolumbicattractionforces.SolidAluminum(Al)Metalsolidbecausealuminumisametal.
Macroscopic:Shiny,silvercoloredmetal.DuctileandMalleable.Highmeltingpoint.Microscopic:Aluminumnucleisurroundedbyafluid“seaofelectrons”SolidNaphthalene(C10H8)Molecularsolid(whenissolidphase)because:non‐metals,MPlow.
Macroscopic:Whitecrystal.Smellslikemothballs.Microscopic:Heldtogetherbydispersionforces.
Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
LiquidWater(H20)Molecularsolid(wheninsolidphase)because:non‐metals,MPlow.
Macroscopic:Clear,odorless,highboilingpoint.Microscopic:Heldtogetherbyhydrogen‐bonding,dipole‐dipoleanddispersionforces.
LiquidEthylAcetate(CH3COOCH2CH3)
Molecularsolid(wheninsolidphase)because:non‐metals,MPlow.
Macroscopic:Clear,nailpolishsmell,lowboilingpoint.Microscopic:Heldtogetherbydipole‐dipoleanddispersionforces.
Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
LiquidHexanes(C6H14)Molecularsolid(wheninsolidphase)because:non‐metals,MPlow.
Macroscopic:Clear,gasolinesmell,lowboilingpoint.Microscopic:Heldtogetherbydispersionforces.LiquidFormaldehyde(CH20)Molecularsolid(wheninsolidphase)because:non‐metals,MPlow.
Macroscopic:Clear,pungentsmell,lowboilingpoint.Microscopic:Heldtogetherbydipole‐dipoleanddispersionforces.
Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
PropertiesofLiquids
1. RankthefollowingcompoundsbyBP,fromlowesttohighest:glucose,ethanol,H2O. Ethanol,water,glucose
2. Rankthefollowingcompoundsbyvaporpressure,fromlowesttohighest:hexane,hexanol,hexanal.
Hexanol,hexanal,hexane
3. Rankthefollowingcompoundsbyviscosity,frommostviscoustoleast:C5H12,CH4,C3H8,C2H6,C4H10.
C5H12,C4H10,C3H8,C2H6,CH4
Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
4. RankthefollowingcompoundsbySurfaceTension,fromlowesttohighest:CHBr3,CHF3,CHCl3.
CHF3,CHCl3,CHBr3
5. RankthefollowingcompoundsbystrengthofIMFs:C2H6,H2O,CH4,NH3.ThensayhoweachofthefollowingsolutionpropertiesvarieswithIMFstrength.
CH4,CH6,NH3,H2O
a. Boilingpoint:WithhigherIMFs,moleculesaremoreattractedtoeachotherandthereforeittakesmoreenergyforonemoleculetomovefromtheliquidphaseintothegasphase.Thus,BPincreaseswithincreasingIMFs.
b. Viscosity:Sinceviscosityisresistancetoflow,thegreatertheattractionbetweenmolecules,themoreresistantitistoflow,andthehighertheviscosity.
c. Vaporpressure:Vaporpressureistheforceofthemoleculesofthesubstanceinthevaporphasepushingdownontheliquidphase.SinceittakesincreasingenergytoremoveamoleculefromtheliquidphaseasIMFsincrease,therewillbefewermoleculesinthegasphaseandthusthevaporpressurewillbelower.
d. Surfacetension:Surfacetensionistheresistanceofaliquidtoincreasingitssurfacearea.Thus,withincreasingIMFs,surfacetensionincreases.
PropertiesofSolids
1. Whattypeofsolidareeachofthese?Whydoyouthinkthis?a. Methane:molecular,becauseitismadeupofallnon‐metalsandhasa
relativelylowMP(‐187°C)
b. Sulfurdioxide:molecular,becauseitismadeupofallnon‐metalsandhasarelativelylowMP(‐187°C)
Revised SH 7/9/13 © LaBrake & Vanden Bout 2013
c. Iron:metal,becauseIron(Fe)isametal
d. Graphite:covalentornetwork,becauseitismadeupofallnon‐metalsandhasarelativelyhighMP(around3652–3697°C)
e. Silicondioxide:covalentornetwork,becauseitismadeupofallnon‐metals
andhasarelativelyhighMP(around1600–1725°C)
f. CalciumBromide:ionic,becauseitismadeupofametalandanon‐metal
g. Lithium:metal,becauseLithium(Li)isametal
2. ArrangethecompoundsBaCl2,diamond,H2,HFinorderofincreasingexpectedMPs. H2,HF,BaCl2,diamond (molecularsolidwithonlydispersionforces,molecularsolidwithhydrogen bonding,ionicsolid,networksolid).