Chemical Chemical Properties of Properties of

WaterWater

• A liquid over A liquid over

71% of the 71% of the

earthearth

• Water molecules =Water molecules =asymmetricalasymmetrical is is shape with the two hydrogen shape with the two hydrogen molecules at one endmolecules at one end

– Separated by Separated by 105105oo when in the when in the gaseous or liquid phasegaseous or liquid phase

– 109.5109.5oo when ice. when ice.

Polar StructurePolar Structure

Polar StructurePolar Structure

Electronegativity of H20Electronegativity of H20

• Unique properties good for living Unique properties good for living things:things:– Hydrogen bondsHydrogen bonds

(affects all other (affects all other properties)properties)

– AdhesionAdhesion and and CohesionCohesion allow it to allow it to travel up a plant, creating:travel up a plant, creating:

°Capillary ActionCapillary Action

Properties of WaterProperties of Water

Capillary ActionCapillary Action• Glass has polar Glass has polar

molecules.molecules.• Glass can Glass can

hydrogen bond.hydrogen bond.• Attracts the water Attracts the water

molecules.molecules.• Some of the pull is Some of the pull is

up.up.

MeniscusMeniscus• Water curves up Water curves up

along the side.along the side.• This makes the This makes the

meniscus.meniscus.

Surface TensionSurface Tension• Water dropsWater drops are are

round because round because all the all the molecules on molecules on the edge are the edge are pulled to the pulled to the middle.middle.

Properties of WaterProperties of Water• Surface tensionSurface tension

– Cohesion between water Cohesion between water molecules form a skin-like molecules form a skin-like

surfacesurface

Properties of WaterProperties of Water• Surface tensionSurface tension

– Can support animals like “water Can support animals like “water striders in pondsstriders in ponds

Properties of WaterProperties of Water• High heat capacityHigh heat capacity, amount of heat , amount of heat

needed to raise the temperature of needed to raise the temperature of one gram of water 1one gram of water 1ooC.C.

• Greater solvent powerGreater solvent power than any other substance. than any other substance.

Properties of WaterProperties of WaterStores much energy as heatStores much energy as heat• Changes temperature Changes temperature slowlyslowly• Maintains Maintains HOMEOSTASISHOMEOSTASIS

High heat of fusionHigh heat of fusion• Temp at which liquid turns solidTemp at which liquid turns solid

High heat of vaporizationHigh heat of vaporization• Temp at which liquid turns to gasTemp at which liquid turns to gas

Stores much energy as heatStores much energy as heat• Changes temperature Changes temperature slowlyslowly• Maintains Maintains HOMEOSTASISHOMEOSTASIS

– Important for ocean habitatImportant for ocean habitat

Properties of WaterProperties of Water

Change of StateChange of State

Dipole StructureDipole Structure• Ice floats in water because all ice Ice floats in water because all ice

molecules are held in molecules are held in hexagonshexagons• Center is open Center is open

space, making space, making ice ice 8% less 8% less dense dense than than water. water.

Dipole StructureDipole Structure• Floating ice Floating ice insulates insulates water below, water below,

preventing freezing: critical for preventing freezing: critical for ocean animalsocean animals

Maximum density: Maximum density: 3.983.98ooCC • Below this temp, form hexagonal Below this temp, form hexagonal

polymers and decrease densitypolymers and decrease density• Above this, molecules are energetic, Above this, molecules are energetic,

move farther apart, decreasing densitymove farther apart, decreasing density

Solvent PropertiesSolvent Properties• Water dissolves salts by surrounding the Water dissolves salts by surrounding the

atoms in the salt molecule and neutralizing atoms in the salt molecule and neutralizing the ionic bond holding the molecule the ionic bond holding the molecule togethertogether

Acids, Bases & SaltsAcids, Bases & Salts• AcidsAcids = compounds (or ions) that react with = compounds (or ions) that react with

water to produce hydrogen ions (Hwater to produce hydrogen ions (H++))

• BasesBases = compounds that yield the hydroxide = compounds that yield the hydroxide ion (OH-) in water solutions. ion (OH-) in water solutions.

• SaltsSalts = ionic compounds that are generally = ionic compounds that are generally formed by the reaction of an acid and a base:formed by the reaction of an acid and a base:

Measuring AcidityMeasuring AcidityHYDRONIUM IONSHYDRONIUM IONS HYDROXIDE IONSHYDROXIDE IONS = H+ ions = OH‑ ions= H+ ions = OH‑ ions

Acid FormationAcid Formation

• SOSO22 + H + H22O --->O --->HH22SO4SO4-2-2 (Sulfuric acid)(Sulfuric acid)

• NONO2 2 + H+ H220 --->0 --->HNOHNO33-- (Nitric acid) (Nitric acid)

Measuring AcidityMeasuring Acidity• pH scalepH scale (log scale) (log scale)–normal rain water (pH of 5-6) COnormal rain water (pH of 5-6) CO22

+ H+ H22O -----> HCOO -----> HCO33--

– pH of acid rain is between pH of acid rain is between 3-43-4

Measuring AcidityMeasuring Acidity

pH - Percent HydroniumpH - Percent Hydronium• Related to the amount of CORelated to the amount of CO22

dissolved in water dissolved in water

– COCO22 combines with the water to combines with the water to

produce carbonic acid which produce carbonic acid which releases Hreleases H++ ions. ions.

HH22COCO33 -------------> H -------------> H++ + + HCOHCO33 - -

CARBONIC ACIDCARBONIC ACID HYDRONIUM BICARBONATE HYDRONIUM BICARBONATE

ION ION IONION

BuffersBuffers• Dissolved CODissolved CO22 in water acts as a in water acts as a

buffer, a substance that buffer, a substance that prevents prevents large shifts in pH.large shifts in pH.

Buffer SystemsBuffer SystemsCOCO22 + H + H22O O H H22COCO33

HH++ + + HCOHCO33--

HH++ + + COCO33-2-2

HH22COCO33 is carbonic acid, is carbonic acid,

HH+ + is the hydronium ion is the hydronium ion

HCOHCO33-- is the bicarbonate ion is the bicarbonate ion

COCO33-2-2 is the carbonate ion is the carbonate ion

Buffer SystemsBuffer SystemsCOCO22 + H + H22O O H H22COCO33

HH++ + + HCOHCO33--

HH++ + + COCO33-2-2

• Adding COAdding CO22 shifts the reaction to shifts the reaction to

the the right right and produces more Hand produces more H++ ions making the water more acid.ions making the water more acid.

Buffer SystemsBuffer SystemsCOCO22 + H + H22O O H H22COCO33

HH++ + + HCOHCO33--

HH++ + + COCO33-2-2

• Removing CORemoving CO22 shifts the reaction shifts the reaction

to the to the left,left, combining H combining H++ ions with ions with carbonate and bicarbonate ions carbonate and bicarbonate ions reducing the acidity.reducing the acidity.

Ocean BuffersOcean Buffers

Designed byDesigned by

Anne F. MabenAnne F. Maben

These images are forThese images are forviewing only and may notviewing only and may not

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