Extraordinary WaterExtraordinary Water

WaterWater

•A water molecule (H2O), is made up of threethree atoms --- one oxygen and two hydrogen.

H

HO

Water is PolarWater is Polar

• In each water molecule, the oxygen atom attracts moreoxygen atom attracts more than its "fair share" of electronselectrons

• The oxygenoxygen end “acts” negativenegative• The hydrogenhydrogen end “acts” positivepositive• Causes the water to be POLARPOLAR• The water molecule itself is

neutralneutral (equal number of e- and p+) --- Zero Net ChargeZero Net Charge

Hydrogen Bonds Exist Hydrogen Bonds Exist Between Water MoleculesBetween Water Molecules• Formed between the Formed between the

negative side negative side of a of a polar molecule and polar molecule and the positive the positive HydrogenHydrogen

• OneOne hydrogen bond hydrogen bond is is weakweak , but , but manymany hydrogen bonds are hydrogen bonds are strongstrong

Interaction Between Interaction Between Water MoleculesWater Molecules

Negative Oxygen Negative Oxygen end of one water molecule is end of one water molecule is attracted to the attracted to the Positive Hydrogen Positive Hydrogen end of end of

another water molecule to form a another water molecule to form a HYDROGEN HYDROGEN BONDBOND

What are What are the the

PropertieProperties of s of

Water?Water?

Properties of WaterProperties of Water

•Universal SolventUniversal Solvent

Properties of WaterProperties of Water

•Universal SolventUniversal Solvent•CohesionCohesion

Properties of WaterProperties of Water

•Universal SolventUniversal Solvent•CohesionCohesion•AdhesionAdhesion

Properties of WaterProperties of Water

•Universal SolventUniversal Solvent•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat

Properties of WaterProperties of Water

•Universal SolventUniversal Solvent•CohesionCohesion•AdhesionAdhesion•High Specific HeatHigh Specific Heat•Less Dense as a SolidLess Dense as a Solid

Solvent – a substance that dissolves another

•Water is called the universal solvent because it dissolves many substances easily so that they can be transported by the blood or other bodily fluids.

•Water is found in and around our cells.

CohesionCohesion• Attraction between particles of Attraction between particles of

the same substance the same substance (( why water why water is attracted to itself)is attracted to itself)

• Results in Results in Surface tensionSurface tension (a (a measure of the strength of watermeasure of the strength of water’’s surface)s surface)

• Produces a Produces a surface film surface film on water on water that that allows insects to walk on allows insects to walk on the surfacethe surface of water of water

Cohesion …Cohesion …

Helps insects walk across water

AdhesionAdhesion• Attraction between two different Attraction between two different

substancessubstances..• Water will make Water will make hydrogen bonds with hydrogen bonds with

other surfacesother surfaces such as glass, soil, plant such as glass, soil, plant tissues, and cotton. tissues, and cotton.

• CapillaryCapillary actionaction-water molecules will -water molecules will ““towtow”” each other along when in a thin each other along when in a thin glass tube.glass tube.

• Example: Example: transpirationtranspiration process which process which plants and trees remove water from plants and trees remove water from the soil, and paper towels soak up the soil, and paper towels soak up water.water.

Adhesion Causes Water to Adhesion Causes Water to … …

Form spheres & hold onto

plant leaves

Attach to a silken spider

web

Adhesion Causes Adhesion Causes Capillary ActionCapillary Action

Which gives water the ability to “climb”

structures

Adhesion Causes Adhesion Causes Capillary Action in Capillary Action in

PlantsPlants

High Specific HeatHigh Specific Heat• Amount of heatAmount of heat needed to raise needed to raise

or lower or lower 1g1g of a substance of a substance 1° C1° C..

• Water Water resistsresists temperature temperature changechange, both for heating and , both for heating and cooling.cooling.

• Water can absorb or release large Water can absorb or release large amounts of heat energy with little amounts of heat energy with little change in actual temperature.change in actual temperature.

High Specific HeatHigh Specific Heat

When is the water warm enough to swim?

How long will it take for this coffee to cool?

Water is Less Dense as Water is Less Dense as a Solida Solid

• Ice is less denseIce is less dense as a solid than as a liquid (ice floats)

• Liquid water has hydrogen hydrogen

bonds bonds that are constantly being constantly being

broken and reformed.broken and reformed.

• Frozen waterFrozen water forms a crystal-like crystal-like

latticelattice whereby molecules are set at fixed distances.

Water is Less Dense as Water is Less Dense as a Solida Solid

•Which is ice and which is Which is ice and which is

water?water?

Water is Less Dense as a Water is Less Dense as a SolidSolid

WaterWater IceIce

Water is Less Dense as Water is Less Dense as a Solida Solid

Ice Floats

Ice protects Ice protects against against temperature temperature

extremes extremes ((insulatesinsulates frozen frozen lakes)lakes)

WaterWater• At sea level, pure water At sea level, pure water boils at boils at

100 °C100 °C and and freezes at 0 °Cfreezes at 0 °C. .

• The The boiling temperature of water boiling temperature of water decreases at higher elevations decreases at higher elevations (lower atmospheric pressure). (lower atmospheric pressure).

• For this reason, an For this reason, an eggegg will take will take longer to boil longer to boil at higher altitudesat higher altitudes

Water is necessary Water is necessary for Homeostasisfor Homeostasis

• Ability to maintain a Ability to maintain a steady state steady state despite changing conditionsdespite changing conditions

• Water is important to this Water is important to this process because:process because:a. Makes a a. Makes a good insulatorgood insulatorb. Resists temperature changeb. Resists temperature changec. c. Universal solventUniversal solventd.d.CoolantCoolant

Solutions & Solutions & SuspensionsSuspensions

• Water is usually part of a Water is usually part of a mixture.mixture.

• There are two types of There are two types of mixtures:mixtures:– SolutionsSolutions– SuspensionsSuspensions

SolutionSolution

• Ionic compounds disperse as Ionic compounds disperse as ionsions in waterin water

• Evenly distributedEvenly distributed• SOLUTESOLUTE

– Substance that is being Substance that is being dissolveddissolved

• SOLVENTSOLVENT– Substance into which the solute Substance into which the solute

dissolvesdissolves

SolutionSolution

SuspensionsSuspensions

• Substances that dondon’’t dissolve t dissolve but separate but separate into tiny pieces.

• Water keeps Water keeps the pieces the pieces suspended suspended so they don’t settle out.

Acids, Bases and pHAcids, Bases and pHOne water molecule One water molecule in 550 million in 550 million

naturally naturally dissociatesdissociates into a into a Hydrogen Ion Hydrogen Ion (H+) (H+) and a Hydroxide and a Hydroxide Ion Ion (OH-)(OH-)

Hydrogen Ion Hydroxide IonHydrogen Ion Hydroxide Ion Acid Acid BaseBase

H2O H+ + OH-

The pH ScaleThe pH Scale• Indicates the concentration of Hconcentration of H++

ionsions• Ranges from 0 – 140 – 14• pH of 7 is neutral7 is neutral• pH 0 up to 7 is acid 0 up to 7 is acid … H+ • pH above 7 – 14 is babove 7 – 14 is basic… OH- • Each pH unit represents a factor

of 10X 10X change in concentration• pH 3 is 10 x 10 x 10 (1000) pH 3 is 10 x 10 x 10 (1000)

stronger than a pH of 6stronger than a pH of 6

AcidsAcids

• StrongStrong Acids Acids have a have a pH of pH of 1-31-3

• Produce Produce lots of lots of H H+ + ionsions

BasesBases

• Strong Strong Bases Bases have a pH of 11 to 14 11 to 14

• Contain lots of OHlots of OH--

ions ions and fewer H+ ions

BuffersBuffers• Weak acids or bases that react Weak acids or bases that react

with strong acids or bases to with strong acids or bases to prevent sharp, sudden changes prevent sharp, sudden changes in pH in pH (neutralization).(neutralization).

• Produced naturally by the body Produced naturally by the body to maintain homeostasisto maintain homeostasis

Weak AcidWeak Acid Weak BaseWeak Base

High Heat of High Heat of VaporizationVaporization

• Amount of energy to convert 1g Amount of energy to convert 1g or a substance from a or a substance from a liquid to a liquid to a gasgas

• In order for water to evaporate, In order for water to evaporate, hydrogen bonds must be brokenhydrogen bonds must be broken..

• As water evaporatesAs water evaporates, it removes a , it removes a lot of lot of heatheat with it. with it.

• Water vapor Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm.

• Heat radiated from the sun Heat radiated from the sun warmed surface of the earth is

absorbed and held absorbed and held

by the vaporby the vapor.

High Heat of High Heat of VaporizationVaporization

• Water's heat of vaporization is 540 cal/g.540 cal/g.

• In order for water to In order for water to evaporateevaporate, , each gram must each gram must GAIN 540 GAIN 540 calories (temperature doesncalories (temperature doesn’’t t change --- 100change --- 100ooC).C).

• As water evaporatesAs water evaporates, it removes , it removes a lot of a lot of heatheat with it with it (cooling (cooling effect)effect)..