Properties of Water and pHProperties of Water and pH

Section 2-2Section 2-2

NotesNotes

LabLab

• Covers Covers three fourthsthree fourths of our planet of our planet

• Most Most abundantabundant compound in living compound in living thingsthings

• Liquid at Liquid at room temproom temp

• ExpandsExpands as it freezes as it freezes

• LighterLighter than most gases than most gases

• ModeratesModerates temperatures temperatures by storing by storing heatheat

Water – an Water – an unusualunusual compoundcompound

Water = HWater = H22OO

• CovalentCovalent bonds hold the bonds hold the molecule togethermolecule together

• ElectronsElectrons are shared are shared unequallyunequally

• Oxygen takes most of Oxygen takes most of the the negativenegative charge charge

• Hydrogen atoms are left Hydrogen atoms are left slightly slightly positivepositive

PolarityPolarity• Molecule has a Molecule has a positivepositive side and a side and a

negativenegative side side– Due to unequal Due to unequal sharingsharing of electrons of electrons

• WeakWeak bonds form bonds form– Called: Called: hydrogenhydrogen bonds bonds

PolarityPolarity

• These These weakweak hydrogen hydrogen bonds are importantbonds are important

• Causes water to Causes water to attractattract other molecules other molecules

• Water’sWater’s hydrogen can hydrogen canbond with up to bond with up to 44 other other moleculesmolecules

Water has special properties Water has special properties due to due to hydrogenhydrogen bonding bonding• CohesionCohesion – attraction between water – attraction between water

moleculesmolecules– Surface tensionSurface tension– Flow of waterFlow of water

• Adhesion Adhesion – attraction – attraction between water and otherbetween water and othermoleculesmolecules– Water sticking to Water sticking to windshieldwindshield

• CapillaryCapillary action – action – movement of water against movement of water against the pull of the pull of gravitygravity– Within plant Within plant stemsstems

IonizationIonization

• Any process by which Any process by which electrically neutralelectrically neutral atoms or molecules are atoms or molecules are convertedconverted to to electrically electrically chargedcharged atoms or molecules atoms or molecules (ions)(ions). .

• Causes molecules to Causes molecules to separateseparate into into simplersimpler molecules, atoms, or ionsmolecules, atoms, or ions

• Water Water attracts other ionsattracts other ions – Conduction of nerve impulsesConduction of nerve impulses– Contraction of musclesContraction of muscles– Digestion of foodDigestion of food

Ionization of WaterIonization of Water

• An Acid has more H+ ions than OH- An Acid has more H+ ions than OH- ions.ions.

• A base has more OH- ions than H+ A base has more OH- ions than H+ ions.ions.

• A neutral solution has an equal A neutral solution has an equal number of each.number of each.

H+ H+ H+ H+OH- OH-

H+ H+OH- OH- OH- OH-

H+ H+ H+ H+OH- OH- OH- OH-

pH = “Power of Hydrogen pH = “Power of Hydrogen Ion”Ion”• Indicates the Indicates the concentrationconcentration of of HH++ ions ions

in solutionin solution• Range = Range = 0 – 140 – 14• pH 7 = pH 7 = neutralneutral • Each pH is Each pH is 10x10x the concentration of the concentration of

the previousthe previous

pH = “Power of pH = “Power of Hydrogen Ion” Hydrogen Ion”• Example:Example:

– Change in pH from Change in pH from 10 to 1210 to 12

– concentration change concentration change equals…equals…

– 10 x 1010 x 10 or… or…– 100100

Acids vs. BasesAcids vs. Bases

ACIDSACIDS BASESBASES

pH pH < 7< 7 pH pH > 7> 7

SourSour taste taste taste taste bitterbitter

more more HH+ + ionsions more more OHOH- - ionsions

pH ScalepH Scale

AcidAcid BaseBase

00

77

1414

[H[H++] pH] pH

10-14 14

10-13 13

10-12 12

10-11 11

10-10 10

10-9 9

10-8 8

10-7 7

10-6 6

10-5 5

10-4 4

10-3 3

10-2 2

10-1 1

100 0

1 M NaOH

Ammonia(householdcleaner)

BloodPure waterMilk

VinegarLemon juiceStomach acid

1 M HCl

Aci

dic

N

eutr

al

Bas

ic

Most living organisms prefer a neutral pH range from 6.5-8.5.

Most life dies in an environment of pH12 or higher.

BuffersBuffers

• Chemicals that Chemicals that neutralizeneutralize small small amounts of amounts of acids or basesacids or bases

• Controls pHControls pH which is which is important to maintaining important to maintaining homeostasishomeostasis

• MinimizesMinimizes shifts in pH shifts in pH

• Normal pH in humans Normal pH in humans is is 6.5 – 7.56.5 – 7.5

Oven cleaner

Bleach

Ammonia solution

Soap

Sea water

Human bloodPure water

Normal rainfall

Acid rainTomato juice

Lemon juice

Stomach acid

Neutral

Incr

easi

ng

ly B

asic

Incr

easi

ng

ly A

cid

ic

Milk

Sodium hydroxideLye

Asprin

Intestinal fluid

Cola

Battery acid

Baking soda

Milk of Magnesia

Urine

Spinach

Tums

Mixture Mixture

• 2 or more 2 or more elementselements or or compoundscompounds mixed together mixed together

• NOT NOT chemicallychemically combined combined

• e.g. e.g. – SoilSoil– AirAir– Salt waterSalt water

Two types of mixturesTwo types of mixtures1. 1. SolutionSolution: 1 or more dissolved : 1 or more dissolved

chemicalschemicals•SolventSolvent – chemical that others dissolve in – chemical that others dissolve in

•Solute – chemical that is Solute – chemical that is dissolveddissolved

• WaterWater is the best solvent!!! is the best solvent!!!

• AqueousAqueous solutions – solutions – solutions of watersolutions of water

Cl-

Water

Cl-

Na+

Water

Na+

2. Suspensions2. Suspensions

• Substances mixed in Substances mixed in waterwater, but , but notnot dissolveddissolved

• MoleculesMolecules are “suspended” in the water are “suspended” in the water

• e.g. e.g. – BloodBlood contains proteins contains proteins

and cellsand cells– CytoplasmCytoplasm contains contains

organelleorganelle

Blood

Cytoplasm

Importance of Water Importance of Water to Living Organismsto Living Organisms

• Most abundant compound in living matterMost abundant compound in living matter

• Universal solvent - dissolves many thingsUniversal solvent - dissolves many things

• Needed for biological (metabolic) reactionsNeeded for biological (metabolic) reactions

• Transports materialsTransports materials

• Regulates temperatureRegulates temperature

• Needed to eliminate wastesNeeded to eliminate wastes

• Protects and cushions vital organsProtects and cushions vital organs

• Lubricates joints and tissuesLubricates joints and tissues

• Reservoir of HReservoir of H++ and OH and OH- - ionsions