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).