The Extraordinary Properties The Extraordinary Properties of Waterof Water

Where there’s life……there’s water!!!

WaterWater• A water molecule (H2O), is made up

of threethree atoms --- one oxygenoxygen and two hydrogenhydrogen. H

HO

Water is Water is PolarPolar• Having positivelypositively and

negativelynegatively charged sides.

• The oxygenoxygen end “acts” negativenegative

• The hydrogenhydrogen end “acts” positivepositive

•The term “POLARITY” means the molecule has an uneven distribution of electrons

What are What are the the

Properties Properties of Water?of Water?

The Universal Solvent

Properties of WaterProperties of Water

• CohesionCohesion

• AdhesionAdhesion

Cohesion – “Co” meansCohesion – “Co” means“With or Together”“With or Together”

• Attraction betweenAttraction between similarsimilar substancessubstances

(( why water is attracted to itself)why water is attracted to itself)

• Due to Due to HydrogenHydrogen bondsbonds

Cohesion Cohesion • Produces a surface film on water called Produces a surface film on water called • surface tensionsurface tension that allows insects to that allows insects to

walk on water and leaves to float.walk on water and leaves to float.• Surface Tension - a measure of the Surface Tension - a measure of the

strengthstrength of water’s of water’s surfacesurface

AdhesionAdhesion• Attraction of HAttraction of H22O to O to

differentdifferent substances substances..• Due to Due to hydrogen hydrogen

bondsbonds

• Ex:paper towels Ex:paper towels soak up water, soak up water, meniscus in a meniscus in a graduated cylinder.graduated cylinder.

Adhesion Also Causes Water to …Adhesion Also Causes Water to …

Form spheres & hold onto

plant leaves

Attach to a silken spider

web

Both Cohesion and Adhesion Both Cohesion and Adhesion Causes Causes

Capillary ActionCapillary Action

Capillary action gives water the ability to “climb”

structures

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

temptemp ofof 1g of H1g of H22O 1° CO 1° C..

• Water has a very Water has a very HIGHHIGH specific specific heat.heat.

• Crucial in temperature stabilityCrucial in temperature stability in in living systems to maintain living systems to maintain homeostasis.homeostasis.

High Heat of VaporizationHigh Heat of Vaporization

• Amount of energy to convert 1g Amount of energy to convert 1g water from a water from a liquid to a liquid to a gas.gas.

• Called Called vaporization vaporization oror evaporationevaporation

High Heat of VaporizationHigh Heat of Vaporization• As water evaporates, it removes a As water evaporates, it removes a

lot of lot of heatheat with it (cooling effect). with it (cooling effect).

• Ex: evaporation of Ex: evaporation of sweatsweat from the from the bodybody

Water is Less Dense as a SolidWater is Less Dense as a Solid• Ice is Ice is less denseless dense

as a solid than as

a liquid –

therefore it floats

• Other materials

contract when

they solidify, but

water expands.

Water is Less Dense as a SolidWater is Less Dense as a Solid

•Which is ice and which is water?Which is ice and which is water?

WaterWater IceIce

Water is a SolventWater is a Solvent• Solvent:Solvent: any substance that dissolves any substance that dissolves

other substances.other substances.• Water is aWater is a veryvery versatileversatile solventsolvent• Other Other polarpolar substances dissolve easily in substances dissolve easily in

water.water.

SolutionSolution• Mixture of Mixture of 2 or more substances. 2 or more substances.

• Evenly distributedEvenly distributed

+ +

MIXTUREMIXTUREMaterials composed of 2 or more elements or compounds that are physically mixed but not chemically combined.

Hydrophilic (“water-loving” )

• substances that dissolve easily in water are known as water soluble.

• Examples: salts, polar compounds (sugar).

Hydrophobic (means “water-fearing”)

• substances that do not dissolve easily in water separate and are known as insoluble..

• Examples: oils, fats, lipids, waxes.

• These substances are non-polar.

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

naturally dissociates into a naturally dissociates into a Hydrogen Ion (HHydrogen Ion (H++) and a Hydroxide ) and a Hydroxide Ion (OHIon (OH--))

Hydrogen Ion Hydroxide Hydrogen Ion Hydroxide IonIon

Acid Acid BaseBase

H2O H+ + OH-

The pH ScaleThe pH Scale• Ranges from 0 to 14

• Measures strength of an acid or base by concentration of H+ ions and OH- ions.

• Pure Water has a pH level of 7.

AcidsAcids• Substance that contains high concentration of H+ ions.

• pH of acids range from 0-6

• Strong acids have a pH of 1-3

BasesBases• Substance that have lower concentrations of H+ ions thus increasing OHOH- - ionsions

• Bases have a pH value range from 8 to 14.

• Strong Bases have a pH of 11 to 14

BuffersBuffers• Weak acids or bases that react with

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

• Produced naturally by the body to Produced naturally by the body to maintain maintain homeostasishomeostasis

Weak AcidWeak Acid Weak Weak BaseBase