The Chemistry of Life Properties of Water copyright cmassengale

The Chemistry of Life

Properties of Water

copyright cmassengale

The Water Molecule

• Neutral Charge – ZERONeutral Charge – ZERO•Have no charge•Have an Equal number of p+ and e-•Charges aren’t evenly distributed


The Water MoleculeThe Water Molecule• PolarityPolarity

– A water molecule is polar because there is an uneven distribution of uneven distribution of electronselectrons between the oxygen and hydrogen atoms.

(-)

(+)


Hydrogen BondsHydrogen Bonds• Polar water molecules Polar water molecules act like act like

magnetsmagnets and attract each other and attract each other • Hydrogen BondsHydrogen Bonds

– The attraction of the Hydrogen The attraction of the Hydrogen end (+) of one molecule for the end (+) of one molecule for the Oxygen end Oxygen end (-)(-) of another water of another water molecule.molecule.

• They are strong bonds that They are strong bonds that form form between moleculesbetween molecules ( (COCO22, H, H22O, O, …)…)


Hydrogen BondsHydrogen Bonds


CohesionCohesion• The attraction

between molecules of the same substance (e.g. water).

• HH22O attracting other O attracting other HH22O moleculesO molecules

• Allows some insects and spiders to walk on water.


Adhesion & CapillarityAdhesion & Capillarity• AdhesionAdhesion - Attraction between - Attraction between

HH22O molecules and different O molecules and different moleculesmolecules

• Cohesion & adhesion produceCohesion & adhesion produce CapillarityCapillarity (upward movement (upward movement against gravity of water through against gravity of water through small tubes)small tubes)Question: How do Question: How do plants make use plants make use of Capillarity?of Capillarity?


Solutions & Solutions & SuspensionsSuspensions

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

• Because so many things Because so many things dissolve in water, it is called dissolve in water, it is called the the Universal SolventUniversal Solvent

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


Properties of SolutionsProperties of Solutions• Ionic compoundsIonic compounds disperse as disperse as ionsions

in water (+ions & -ions spread out in water (+ions & -ions spread out among polar water molecules)among polar water molecules)

• Solutions are Solutions are Evenly distributedEvenly distributed mixturesmixtures

• SOLUTESOLUTE– Substance that is being dissolvedSubstance that is being dissolved

• SOLVENTSOLVENT– Dissolving Substance for the Dissolving Substance for the

solutesolutecopyright cmassengale

Ionic SolutionsIonic Solutions

Na+ ions will be attracted to WHAT END of the water molecule?copyright cmassengale

SuspensionsSuspensions• Substances that Substances that

don’t dissolve but don’t dissolve but separate into tiny separate into tiny pieces.pieces.

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

• Blood & Blood & CytoplasmCytoplasm are are suspensionssuspensions


Acids, Bases & pHAcids, Bases & pH• 1 water molecule in 550 million 1 water molecule in 550 million

naturally dissociates into a naturally dissociates into a Hydrogen IonHydrogen Ion and a and a Hydroxide Hydroxide IonIon

Hydrogen Ion Hydroxide IonHydrogen Ion Hydroxide Ion Acid Acid BaseBase

H2O H+ + OH-


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

ions• Ranges from 0 – 14• pH of 7 is neutral• pH 0 up to 7 acid … H+ • pH above 7 to 14 base… OH- • Each pH unit represents a factor

of 10X change in concentrationHow much stronger is a pH3 than a How much stronger is a pH3 than a

pH of 5?pH of 5?copyright cmassengale

AcidsAcids•Strong

Acid = pH 1-3

•High in H+

ions•Lower

number of OH- ions


BasesBases•Strong Base

= pH 11 – 14•High in OH-

ions•Lower in

number of H+ ions


BuffersBuffers• Weak acids or basesWeak acids or bases that that

react with strong acids or react with strong acids or basesbases

• Made by the bodyMade by the body• Prevent sharp, sudden Prevent sharp, sudden

changes in pH changes in pH (keep pH (keep pH neutral)neutral)

Weak AcidWeak Acid Weak BaseWeak Basecopyright cmassengale


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The Chemistry of Life Properties of Water copyright cmassengale