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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-]