Chapter 3: Chapter 3: WaterWater

Water’s PolarityWater’s PolarityCohesion, moderation of Cohesion, moderation of

temperature, ice is less dense, temperature, ice is less dense, universal solventuniversal solvent

Dissociation of water Dissociation of water moleculesmolecules

pHpH

T.O.D:(table from old study guide)take home essay?

T.O.D:(table from old study guide)take home essay?

WATER:WATER: the stuff of the stuff of life!life!

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Water’s Water’s polarity polarity and and hydrogen hydrogen bondsbonds

Account for its unique properties that Account for its unique properties that contribute to the fitness of Earth’s as contribute to the fitness of Earth’s as an environment for life.an environment for life.

Cohesion/AdhesionCohesion/Adhesion

Cohesion is water’s attraction to Cohesion is water’s attraction to waterwater

Adhesion is water’s attraction to Adhesion is water’s attraction to other substancesother substances

Surface tensionSurface tension Water transport in plants, up ___ Water transport in plants, up ___

tubestubes

Stabilize temperaturesStabilize temperatures

WHY?WHY? High specific heatHigh specific heat Water moderates global and Water moderates global and

organismal temperaturesorganismal temperatures Evaporative cooling is important Evaporative cooling is important

for animals as well as plantsfor animals as well as plants

Expansion Expansion upon freezingupon freezing

Because of Hydrogen bonding …Because of Hydrogen bonding … 00° C ° C Ice is less dense than liquid Ice is less dense than liquid

waterwater When is water most dense?When is water most dense?

If this didn’t happen, bodies of water If this didn’t happen, bodies of water would freeze solidwould freeze solid

Structure of Ice vs liquid Structure of Ice vs liquid waterwater

VersatileVersatileSolvent:Solvent:

Ex: Salt and Ex: Salt and waterwater

Ionic and Ionic and polar com-polar com-pounds pounds dissolve in dissolve in waterwater

Even very large Even very large molecules like molecules like proteins proteins dissolve in dissolve in water as long water as long as there are as there are areas of ionic or areas of ionic or polar bonds.polar bonds.

The pH scaleThe pH scale pH=The measure of pH=The measure of

HH++ and OH and OH-- in a in a solution.solution.

Scale 0-14…Scale 0-14… Acids=increase the Acids=increase the

HH++ concentration concentration Bases=reduce the Bases=reduce the

HH++ concentration concentration

pH = -log[HpH = -log[H++]] Neutral = 10Neutral = 10--

77[H+][H+]

Ex:Ex: pH 9 pH 9 has H has H++ concentration of concentration of 1010-9-9 M and an OH M and an OH-- concentration of concentration of 1010-5 -5 MM

Practice problems…Practice problems…

BuffersBuffers Acid rainAcid rain

Ch.1-4 Quiz study tips:Ch.1-4 Quiz study tips:

Practice questions at the end of Practice questions at the end of the chaptersthe chapters

The test’s CD ROM demonstrations The test’s CD ROM demonstrations and practice questionsand practice questions

Study your HW notes and class Study your HW notes and class notesnotes

SourcesSources

Campbell, Reece, Mitchell. Campbell, Reece, Mitchell. Biology, 5Biology, 5thth Ed. 1999, Chap- Ed. 1999, Chap-ter one. Pgs. 1-21.ter one. Pgs. 1-21.

Campbell, Reece, Mitchell. Campbell, Reece, Mitchell. Biology, 5Biology, 5thth Ed. 1999, Ed. 1999, Presentations CD-ROM.Presentations CD-ROM.

Click art CD-ROM, Click art CD-ROM, Broderbund.Broderbund.

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