lecture atoms molecules water ph sp'13
TRANSCRIPT
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TheChemistryofLife
Learningoutcomes:
Atoms,elements,ma8er,andmolecules
Thefourmainelementsinlife Chemicalbonds Atomicstructure Proper=es(andconsequences)of
water
ThepHscale
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SomeBasicDefini=ons
Ma8er:anythingwithmass. Element:Asubstance
consis=ngofatomswhichall
havethesamenumberofprotons.
Atom:Thebasicunitofanelement.
Molecule:twoormoreatomswhichchemicallycombinetoformasingle
species.
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ChemicalBasisofLife
About96.3%ofthehumanbodyiscomposedofjustFOURelements:
Hydrogen Oxygen Nitrogen Carbon HONC! (restofthe25elementsareconsidered
trace
)
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AtomicStructure
Ifithasadifferentnumberofprotons,itisadifferent
element.
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Isotopes:when#n>#p
Q.Ifyouhave10gramsofcarbon,
andthe1/2lifeofcarbon-14is5730years,howmanygramsof
carbonwouldyourhaveaer
11460years(2x5730years)?
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ectron cstructure eterm nesproper=esofanelement
Thearrangementofelectronsdeterminesthechemicalproper=esofan
element.
Ques=on:Howmanyotheratomscanacarbonatombindto?
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HowmanybondscanNitrogenand
Oxygenform?
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Electronega=vity-anatoms
a8rac=on/loveforitselectron
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POLAR molecule
NON-POLAR molecules
Whatdoeselectronega/vitymeanfor
molecules?
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Howdoelementschemicallycombine?
Ionic Bonds formcompounds
Covalentbonds form
molecules
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Ionicbonds,incontrasttocovalentbonds
doNOTshareelectrons.
Ques=on:Whatdoesthispictureimply
abouttheelectronega=vityofchlorine?
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LifeRequiresWater
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Property1.Waterhasahighspecific
heatcapacityandheatofvaporiza=on.
HeatCapacity:Theamountofheatrequiredtochange
thetemperatureofa
substance. Heatofvaporiza=on:The
amountofheatrequiredto
changefromliquidtogas.
Consequences:Watermoderatestemp.Waterpromotes
evapora=vecooling.
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Property#2Waterhascohesiveness
Cohesiveness:Polarwatermoleculess=ck
together.
Consequence:Waterhashighsurface
tension.
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Property#3:Hydrogenbondingpermits
INCREASEDspacingbetweensolidwater
molecules. Consequence:Solidwaterislessdensethanliquidwater.
Therefore,icefloats.Waterbelowiceisabovefreezingtemps,allowinglifetosurvive.
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Property#4:Waterisauniversalsolvent.
Almostanythingwilldissolveinit.
Consequence:Everythinginacellis
dissolvedinwater.
Thisiswhythesearchforlifeon
otherplanetsbegins
withthesearchforwater.
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ThepHscale
Acidityandbasicityhavean
effectonbiological
processes.
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Furtreesaresuscep=bletoacid
precipita=on
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Ques=ons:
Whatpar=cledeterminestheiden=tyofanelement?
A.Thenumberofelectrons B.Thenumberofneutrons C.Thenumberofprotons
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Howmanychemicalbondscancarbon
make?
A. FourB.ThreeC.TwoD.One
C d th l t h ll
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Canyoudrawtheelectronshells
surroundingacarbonatom?
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Whatisthedifferencebetween
covalentbondingandionicbonding?
A.Covalentbondinginvolvessharingofelectronswhileionicbondinginvolvesthe
stealingofanelectronfromoneatomby
another.
B.Ionicbondinginvolvessharingofelectronswhilecovalentbondinginvolvesthestealing
ofanelectronfromoneatombyanother.
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Isasolu=onwithapHofneutralor
basic?
Basic
I l = th t f H+ i
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Inasolu=on,theamountofH+is
greaterthantheconcentra=onofOH-.
Thesolu=onis:A.[OH-]>[H+]Basic
B.[OH-]