water and the fitness of the environment part ii.emergent properties

Water and the Fitness of Water and the Fitness of the Environmentthe Environment

Part II.Emergent PropertiesPart II.Emergent Properties

You Should Know Chap. 3You Should Know Chap. 3

• The importance of hydrogen bonding The importance of hydrogen bonding to the properties of waterto the properties of water

• Four unique properties of water and Four unique properties of water and how each contributes to life on Earthhow each contributes to life on Earth

• How to interpret the pH scaleHow to interpret the pH scale

• The importance of buffers in The importance of buffers in biological systembiological system

3.2 Ability to Moderate 3.2 Ability to Moderate TemperatureTemperature

• Water absorbs heat from warmer air Water absorbs heat from warmer air and releases stored heat to cooler airand releases stored heat to cooler air

• Water can absorb or release a large Water can absorb or release a large amount of heat with only a slight amount of heat with only a slight change in its own temperaturechange in its own temperature

3.2 Ability to Moderate Temp.-Water’s High Specific Heat3.2 Ability to Moderate Temp.-Water’s High Specific Heat

• The The specific heat specific heat of a substance is the amount of of a substance is the amount of heat that must be absorbed or lost for 1 g of that heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºCsubstance to change its temperature by 1ºC

• The specific heat of water is 1 cal/g/ºCThe specific heat of water is 1 cal/g/ºC• Water resists changing its temperature because of its Water resists changing its temperature because of its

high specific heat because:high specific heat because:– Heat is released when hydrogen bonds formHeat is released when hydrogen bonds form– Heat is absorbed when hydrogen bonds breakHeat is absorbed when hydrogen bonds break

• The high specific heat of water minimizes temperature The high specific heat of water minimizes temperature fluctuations to within limits that permit lifefluctuations to within limits that permit life

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 3-5Fig. 3-5

San Diego 72°

40 miles

Pacific Ocean

70s (°F)

80s

90s

100s

Santa Barbara 73°

Los Angeles (Airport) 75°

Burbank90°

San Bernardino100°

Riverside 96°Santa Ana 84° Palm Springs

106°

3.2 Insulation of Bodies of Water by Floating 3.2 Insulation of Bodies of Water by Floating IceIce

• Ice floats in liquid water because Ice floats in liquid water because hydrogen bonds in ice are more hydrogen bonds in ice are more “ordered,” making ice less dense“ordered,” making ice less dense

• Water reaches its greatest density at 4°CWater reaches its greatest density at 4°C

• If ice sank, all bodies of water would If ice sank, all bodies of water would eventually freeze solid, making life eventually freeze solid, making life impossible on Earthimpossible on Earth


Fig. 3-6Fig. 3-6

Hydrogenbond

Liquid waterHydrogen bonds break and re-form

IceHydrogen bonds are stable

Fig. 3-6aFig. 3-6a

Hydrogenbond

Liquid waterHydrogen bonds break and re-form

IceHydrogen bonds are stable

The Solvent of LifeThe Solvent of Life

• A A solution solution is a liquid that is a is a liquid that is a homogeneous mixture of substanceshomogeneous mixture of substances

• A A solvent solvent is the dissolving agent of a is the dissolving agent of a solutionsolution

• The The solute solute is the substance that is is the substance that is dissolveddissolved

• An An aqueous solution aqueous solution is one in which is one in which water is the solvent water is the solvent


• Water is a versatile solvent due to its Water is a versatile solvent due to its polarity, which allows it to form hydrogen polarity, which allows it to form hydrogen bonds easilybonds easily

• When an ionic compound is dissolved in When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water, each ion is surrounded by a sphere of water molecules called a water molecules called a hydration shellhydration shell


• Water can also dissolve compounds Water can also dissolve compounds made of nonionic polar moleculesmade of nonionic polar molecules

• Even large polar molecules such as Even large polar molecules such as proteins can dissolve in water if they proteins can dissolve in water if they have ionic and polar regionshave ionic and polar regions


Concept 3.3: Acidic and basic conditions Concept 3.3: Acidic and basic conditions affect living organismsaffect living organisms

• A hydrogen atom in a hydrogen bond A hydrogen atom in a hydrogen bond between two water molecules can shift between two water molecules can shift from one to the other:from one to the other:– The hydrogen atom leaves its electron The hydrogen atom leaves its electron

behind and is transferred as a proton, or behind and is transferred as a proton, or hydrogen ion hydrogen ion (H(H++))

– The molecule with the extra proton is now The molecule with the extra proton is now a a hydronium ion hydronium ion (H(H33OO++), though it is ), though it is often represented as Hoften represented as H++

– The molecule that lost the proton is now a The molecule that lost the proton is now a hydroxide ion hydroxide ion (OH(OH––))


Hydrophilic and Hydrophobic Hydrophilic and Hydrophobic SubstancesSubstances

• Hydrophilic-Hydrophilic-waterwater lovingloving

• Hydrophobic-Hydrophobic-water fearingwater fearing

• Oil molecules are hydrophobic Oil molecules are hydrophobic because they have relatively nonpolar because they have relatively nonpolar bondsbonds

• A A colloid colloid is a stable suspension of fine is a stable suspension of fine particles in a liquidparticles in a liquid


Solute Concentration in Aqueous Solute Concentration in Aqueous SolutionsSolutions

• Most biochemical reactions occur in waterMost biochemical reactions occur in water

• Chemical reactions depend on collisions of Chemical reactions depend on collisions of molecules and therefore on the concentration molecules and therefore on the concentration of solutes in an aqueous solutionof solutes in an aqueous solution


• Acidic solutions have pH values less than 7Acidic solutions have pH values less than 7

• Basic solutions have pH values greater Basic solutions have pH values greater than 7than 7

• Most biological fluids have pH values in the Most biological fluids have pH values in the range of 6 to 8range of 6 to 8


Fig. 3-9Fig. 3-9

Neutral solution

Acidic solution

Basic solution

OH–

OH–

OH–

OH–

OH–OH–

OH–

H+

H+

H+

OH–

H+ H+

H+ H+

OH–

OH–

OH–OH–

H+

OH–

H+

H+

H+

H+

H+

H+

H+

OH–

Neutral [H+] = [OH–]

Incr

easi

ng

ly A

cid

ic [

H+]

> [

OH

–]

Incr

easi

ng

ly B

asic

[H

+]

< [

OH

–]

pH Scale0

1

2

3

4

5

6

7

8

Battery acid

Gastric juice,lemon juice

Vinegar, beer,wine, cola

Tomato juice

Black coffee

Rainwater

Urine

SalivaPure water

Human blood, tears

Seawater

9

10

Milk of magnesia

Household ammonia

Householdbleach

Oven cleaner

11

12

13

14

BuffersBuffers

• The internal pH of most living cells The internal pH of most living cells must remain close to pH 7must remain close to pH 7

• Buffers Buffers are substances that minimize are substances that minimize changes in concentrations of Hchanges in concentrations of H++ and and OHOH–– in a solution in a solution

• Most buffers consist of an acid-base Most buffers consist of an acid-base pair that reversibly combines with Hpair that reversibly combines with H++


Threats to Water Quality on Threats to Water Quality on EarthEarth• Acid precipitation Acid precipitation refers to rain, refers to rain,

snow, or fog with a pH lower than 5.6snow, or fog with a pH lower than 5.6

• Acid precipitation is caused mainly by Acid precipitation is caused mainly by the mixing of different pollutants with the mixing of different pollutants with water in the air and can fall at some water in the air and can fall at some distance from the source of pollutantsdistance from the source of pollutants

• Acid precipitation can damage life in Acid precipitation can damage life in lakes and streamslakes and streams

• Effects of acid precipitation on soil Effects of acid precipitation on soil chemistry are contributing to the chemistry are contributing to the decline of some forestsdecline of some forests


• Human activities such as burning fossil Human activities such as burning fossil fuels threaten water qualityfuels threaten water quality

• COCO22 is released by fossil fuel is released by fossil fuel combustion and contributes to:combustion and contributes to:– A warming of earth called the A warming of earth called the

“greenhouse” effect“greenhouse” effect– Acidification of the oceans; this leads to a Acidification of the oceans; this leads to a

decrease in the ability of corals to form decrease in the ability of corals to form calcified reefscalcified reefs


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