Chemistry of Chemistry of LifeLife

Properties of WaterProperties of Water

“Water, water everywhere, and not a drop to drink”

Colbert link

Water Riddles? Guess all Water Riddles? Guess all and win!and win!• 1. 1. You cannot see me, though I am here. Rain comes You cannot see me, though I am here. Rain comes

from me when the days aren’t fair. from me when the days aren’t fair.

• 2. If you want a drink look not to me, I am much too 2. If you want a drink look not to me, I am much too cold and hard you see. cold and hard you see.

• 3. There’s a lot of me around, but still don’t waste, 3. There’s a lot of me around, but still don’t waste, even though I have a very bad taste. even though I have a very bad taste.

• 4. It’s down below most rain does go, I hide in the 4. It’s down below most rain does go, I hide in the earth where I don’t show. earth where I don’t show.

• 5. I’m the water most you see, I stand around or 5. I’m the water most you see, I stand around or sometimes flow free. sometimes flow free.

Water vapor

Ice water

Salt water

Ground water

Fresh water

How much of the Earth’s How much of the Earth’s water is fresh water?water is fresh water?

It seems like there is a lot of water on earth It seems like there is a lot of water on earth – this is true, but only about 3% of it is – this is true, but only about 3% of it is freshwater. Most of the freshwater is ice. A freshwater. Most of the freshwater is ice. A great reason to keep our lakes, streams, great reason to keep our lakes, streams, rivers and groundwater clean.rivers and groundwater clean.

Interestingly, human blood and seawater Interestingly, human blood and seawater have about the same salt concentration. have about the same salt concentration. This just a little evidence that life on earth This just a little evidence that life on earth began under water.began under water.

Where did Earth’s water Where did Earth’s water come from?come from?

About 4.55 billion years ago, after the violent birth of the solar system, materials left over began to clump together – including the Earth. Over time, the earth has cooled, and less-dense materials have made their way toward the surface, while the densest materials remain at the core.

The Earth’s distance from the sun makes it perfect for water to exist in liquid form. There are two major hypotheses about how earth got its water:

The “Inside-Out” model proposes that Earth formed with a little water bonded to its minerals. It eventually made its way to the surface through volcanism.

The “Outside-In” model proposes that Earth formed without water, and it arrived here with meteorites and comets that bombarded our young planet.

More about WaterMore about WaterWhy are we studying water?Why are we studying water?

All life occurs in water inside & outside the cell

All life occurs in water inside & outside the cell

Water is essential to all life Water is essential to all life on Earth!on Earth!

• Water makes up about 70% of all living organisms Water makes up about 70% of all living organisms on Earth (almost 90% of body weight!). This is on Earth (almost 90% of body weight!). This is some more evidence that life originated in water. some more evidence that life originated in water. Terrestrial organisms, like humans, have to carry Terrestrial organisms, like humans, have to carry their water with them.their water with them.

• Human brains are about 70% water.Human brains are about 70% water.• Human lungs are nearly 90% water.Human lungs are nearly 90% water.• Human blood is about 83% water.Human blood is about 83% water.To remain alive, an adult human must replace To remain alive, an adult human must replace 2.5 2.5

LitersLiters of water/day. Much of this comes from foods of water/day. Much of this comes from foods that we eat. Humans’ sense of smell, taste and that we eat. Humans’ sense of smell, taste and sight require water, and our alveoli, for gas sight require water, and our alveoli, for gas exchange, always remain moist!exchange, always remain moist!

WaterWater• How do the How do the

unique chemical unique chemical and physical and physical properties of properties of water make life water make life on earth on earth possible??possible??

Bouncy water link

Water makes up Water makes up 70-95%70-95% of all of all cells and covers cells and covers 75%75% of the of the earthearth

• Exists in solid, liquid, Exists in solid, liquid, and gas naturallyand gas naturally

• LIFE EVOLVED IN LIFE EVOLVED IN WATER!!WATER!!

• Water has also been Water has also been found:found:on our moonon our moonon marson marson the moon of Jupiteron the moon of Jupiteroutside our solar systemoutside our solar system

The Polarity of WaterThe Polarity of Water• 2 hydrogen's covalently bonded with 1 2 hydrogen's covalently bonded with 1

oxygenoxygen

• Water is polar = asymmetrical with charges Water is polar = asymmetrical with charges on opposite sideson opposite sides

• Water molecules act like tiny magnetsWater molecules act like tiny magnets

• Hydrogen bonding causes this “magnetism”Hydrogen bonding causes this “magnetism”

Chemistry of waterChemistry of water• HH22O molecules form H-bonds O molecules form H-bonds

with each otherwith each other– ++ attracted to attracted to ––– creates a creates a sticky moleculesticky molecule

1212

Ice, water, vapor

1313

Hydrogen bonding (electric attraction)

Ice Liquid

1414

Surface tension

This attraction between water

molecules gives it many unique properties:

•water is “cohesive”- it has the ability to bind to itself (like surface tension)

•Water is “adhesive” – it

binds well to other things (like glass,

metal, plastic)

•Water can absorb lots of heat without changing temperature, or changing phase (from liquid to gas)

•Water dissolves more substances on earth than any other chemical!

•Water is less dense as a solid than it is as a liquid – this is very rare on earth!

The special case of ice The special case of ice ice floatsice floats!!!!!!

• Most (all?) substances are more dense when they Most (all?) substances are more dense when they are solid, butare solid, but

Not water…it is most dense at Not water…it is most dense at degreesdegrees

• Ice floatsIce floats!!– H bonds form a crystalH bonds form a crystal

And this hasmade all the difference!

4۫ C

Why is “ice floats” Why is “ice floats” important?important?• Oceans & lakes don’t freeze solidOceans & lakes don’t freeze solid

– surface ice insulates water belowsurface ice insulates water below•allowing life to survive the winterallowing life to survive the winter

– if ice sank…if ice sank…•ponds, lakes & even oceans would freeze solidponds, lakes & even oceans would freeze solid• in summer, only upper few inches would thawin summer, only upper few inches would thaw

– seasonal turnover of lakesseasonal turnover of lakes•cycling nutrients in autumncycling nutrients in autumn

Specific heatSpecific heat

• HH22O resists changes in temperatureO resists changes in temperature– high specific heat high specific heat – takes a lot to takes a lot to heatheat it up it up– takes a lot to takes a lot to coolcool it down it down

• HH22O moderates temperatures on EarthO moderates temperatures on Earth

Heat of vaporizationHeat of vaporizationEvaporative Evaporative coolingcooling

Organisms rely on heat of Organisms rely on heat of vaporization to remove body heatvaporization to remove body heat

Evaporative CoolingEvaporative CoolingVaporization= liquidVaporization= liquid gas gasHeat of Vaporization= quantity of heat a liquid must absorb for Heat of Vaporization= quantity of heat a liquid must absorb for

1 g to be converted to gaseous state(2260J/g) 1 g to be converted to gaseous state(2260J/g)

Evaporative coolingEvaporative cooling = = cooling of a liquid’s cooling of a liquid’s surface when the liquid evaporatessurface when the liquid evaporates*as large # of molecules break free and depart, they *as large # of molecules break free and depart, they carry away some energy and decrease water’s surface carry away some energy and decrease water’s surface temp.temp.

Water’s high heat of vaporization:Water’s high heat of vaporization:1.1. Moderates earth’s climateModerates earth’s climate2.2. Stabilizes temp. in aquatic ecosystemsStabilizes temp. in aquatic ecosystems3.3. Helps organisms from overheating by Helps organisms from overheating by

evaporative coolingevaporative cooling

High Surface High Surface TensionTension

• A measure of how A measure of how difficult it is to stretch or difficult it is to stretch or break the surface of a break the surface of a liquidliquid

• Water has a greater Water has a greater surface tension than surface tension than most liquidsmost liquids

• Causes water to beadCauses water to bead• A result of a large A result of a large

amount of amount of • Related to cohesionRelated to cohesion

Hydrogen bonds

Cohesion & AdhesionCohesion & Adhesion• H bonding between HH bonding between H22O molecules is O molecules is

cohesioncohesion– water is “sticky”water is “sticky”

• surface tensionsurface tension

•drinking strawdrinking straw

• H bonding between HH bonding between H22O & O & other substances is other substances is adhesionadhesion– capillary actioncapillary action– meniscusmeniscus– water climbs upwater climbs up

paper towel or clothpaper towel or cloth

Can you sucksugar up a straw?

How does HHow does H22O get to top of trees?O get to top of trees?

Transpiration built on cohesion & adhesion Transpiration built on cohesion & adhesion

Why is this important for the tree?

Water is the solvent of lifeWater is the solvent of life• Polarity makes HPolarity makes H22O a good O a good solventsolvent

– polar Hpolar H22O molecules surround O molecules surround ++ & & –– ionsions

– solventssolvents dissolve dissolve solutessolutes creating creating solutionssolutions

Universal Solvent Universal Solvent “like dissolves “like dissolves like”like”

• SolutionSolution = a liquid that is a = a liquid that is a homogeneoushomogeneous mixture of 2 or more substancesmixture of 2 or more substances

• SolventSolvent = Dissolving agent of the solution = Dissolving agent of the solution• SoluteSolute = Substance dissolved in the = Substance dissolved in the

solutionsolution• Aqueous Aqueous = Solution in which = Solution in which waterwater is the is the

solventsolvent

Water is a Water is a medium for the medium for the

chemical chemical reactions of life~ reactions of life~

METABOLISMMETABOLISM

Do you dissolve in water?Do you dissolve in water?•HydrophilicHydrophilic

– substances have attraction to Hsubstances have attraction to H22OO

– polarpolar or or non-polarnon-polar??

Or don’t you?Or don’t you?•HydrophobicHydrophobic

– substances that don’t have an substances that don’t have an attraction to Hattraction to H22OO

– polarpolar or or non-polarnon-polar??

fat (triglycerol)

Dissociation of Ionic compounds in water

Leads to pH. What is that?

Ionization of water & pHIonization of water & pH•Water ionizesWater ionizes

– HH++ splits off from H splits off from H22O, leaving O, leaving OHOH––

•if [if [HH++]] = [= [--OHOH], water is ], water is neutralneutral

•if [if [HH++]] > [> [--OHOH], water is ], water is acidicacidic

•if [if [HH++]] < [< [--OHOH],], water is water is basicbasic

•pH scale pH scale measure of hydrogen measure of hydrogen ionion– how acid or basic solution ishow acid or basic solution is– 1 1 7 7 14 14 H2O H+ + OH–H2O H+ + OH–

Organisms are sensitive to Organisms are sensitive to changes in pHchanges in pH

• Dissociation (separation into ions) of WATER Dissociation (separation into ions) of WATER molecules. (acids/bases/salts also ionize)molecules. (acids/bases/salts also ionize)

• A equilibrium, most of the water is NOT ionizedA equilibrium, most of the water is NOT ionized

Water’s connection to pH, Water’s connection to pH, Acids and BasesAcids and Bases• Pure water at room temp: [H+] = [OH-]Pure water at room temp: [H+] = [OH-]• Acids have a higher [H+] and bases have Acids have a higher [H+] and bases have

a higher [OH-]a higher [OH-]• The pH scaleThe pH scaleBased on [H+][OH-] = 1.0 x 10 Based on [H+][OH-] = 1.0 x 10 -14-14

pH = -log[H+]pH = -log[H+][H+] = 1.0 x 10[H+] = 1.0 x 10-pH-pH

Scale ranges from 0-14 Scale ranges from 0-14 Measures the amt of H+Measures the amt of H+

pH is a LOG scalepH is a LOG scale each pH uniteach pH unitdifference represents a difference represents a tenfold differencetenfold difference, , so slight changes in pH represents lg. so slight changes in pH represents lg. Change in [H+] Change in [H+]

Practice QuestionPractice Question

• How much greater is the [H+] in a How much greater is the [H+] in a solution with a pH of 2 than in a solution with a pH of 2 than in a solution with a pH of 6?solution with a pH of 6?

2 2 3 3 4 4 5 5 6 6 10 100 1000 10 100 1000 10,00010,000

1001

2

3

4

5

6

7

8

9

3Amount of base added

Bufferingrange

4 52

pH

Buffers & cellular regulationBuffers & cellular regulation• pH of cells must be kept ~7pH of cells must be kept ~7

– pH affects shape of moleculespH affects shape of molecules– shape of molecules affect functionshape of molecules affect function– pH affects cellular functionpH affects cellular function

• Control pH by Control pH by buffersbuffers– reservoir of Hreservoir of H++

•donate H+ when donate H+ when [H[H++] falls] falls

•absorb H+ when absorb H+ when [H[H++] rises] rises

BuffersBuffers• Help to maintain the pH of body fluids within the Help to maintain the pH of body fluids within the

narrow range necessary for lifenarrow range necessary for life• Usually pH 6Usually pH 688• Buffer = Buffer = substance that prevents large sudden substance that prevents large sudden

changes in pHchanges in pH• Are combinations of H+ donor and H+ acceptor Are combinations of H+ donor and H+ acceptor

forms of weak acids or weak basesforms of weak acids or weak bases• Work by accepting H+ ions from solutions when Work by accepting H+ ions from solutions when

they are in excess, and by donating H+ ions to they are in excess, and by donating H+ ions to the solution when they have been depletedthe solution when they have been depleted

• Example:Example:Bicarbonate bufferBicarbonate buffer

Buffers in the BLOOD!“You have been

‘kissed’ at the witching hour and your blood has been depleted of water causing a rise in pH (more hydroxide ions) of blood from normal 7.4 How does equilibrium respond knowing a person cannot survive a shift in blood pH of more than 10-fold?

More carbonic acid dissociates resulting in more H+ (producing more water when it joins with the excess OH-)

ColorlessColorless

• High transmission of High transmission of visible lightvisible light

• Light is able to Light is able to penetrate tissue penetrate tissue

• Light is able to Light is able to penetrate aquatic penetrate aquatic environmentenvironment This is This is great for great for PHOTOSYNTHESIS!!PHOTOSYNTHESIS!!

Light in WaterLight in Water

Why is the Ocean blue?Why is the Ocean blue? The sunlight that strikes the water is absorbed, reflected and The sunlight that strikes the water is absorbed, reflected and

refracted. In the visible spectrum of light, refracted. In the visible spectrum of light, yellowsyellows and and redsreds are are most readily absorbed, while most readily absorbed, while bluesblues are reflected off of water. This are reflected off of water. This makes it appear blue to our eyes.makes it appear blue to our eyes.

Light and waterLight and waterMost of the Sun’s energy that strikes the ocean is absorbed within Most of the Sun’s energy that strikes the ocean is absorbed within the top meter of water. At most, light will only penetrate 1,000 the top meter of water. At most, light will only penetrate 1,000 meters. At the deepest parts of the ocean, this leaves several meters. At the deepest parts of the ocean, this leaves several thousands of meters without any light. How has life adapted? thousands of meters without any light. How has life adapted?

Some Algae produce more chlorophyll at greater depths

Most large fish feed near the surface, where the most food is found

Some fish have their own lights!

Some don’t rely on photosynthesis- these deep sea vent tube worms get their energy from bacteria in their bodies that change chemicals to food.

Sound and waterSound and water• Sound travels five times more efficiently Sound travels five times more efficiently

in water than it does in air. Many in water than it does in air. Many marine organisms use this fact to their marine organisms use this fact to their advantage…advantage…

Some Examples:Some Examples: • Dolphins have evolved a “click language” that they can Dolphins have evolved a “click language” that they can

use to warn others of a predator from miles away.(1)use to warn others of a predator from miles away.(1)• Sperm Whales use sonar called “echolocation” to Sperm Whales use sonar called “echolocation” to

bounce sound off of objects. This helps them to bounce sound off of objects. This helps them to determine size, speed, shape and proximity of objects.determine size, speed, shape and proximity of objects.(2)(2)

• Baleen whales, like humpback whales, have enormous Baleen whales, like humpback whales, have enormous vocal chords that allow them to emit the loudest sounds vocal chords that allow them to emit the loudest sounds on earth! These are complex “songs” that the whales on earth! These are complex “songs” that the whales use to flirt with the opposite sex.(3)use to flirt with the opposite sex.(3)

1

2 3

Water Water CycleCycle

Wow! Looks like a

2nd grader drew this!

He’s gonnaearn a

Darwin Award!

Do one brave thing today…then run like hell!

AnyQuestions?

Deadly Ninja Assassin Deadly Ninja Assassin Attack!Attack!• Groups of 3: one tall, one short, one with Groups of 3: one tall, one short, one with

steady hand to pour watersteady hand to pour water

• 80ml in small beaker of water, string, 80ml in small beaker of water, string, 250ml empty beaker250ml empty beaker

• You must use the string to “poison” your You must use the string to “poison” your teammate (team that loads the most teammate (team that loads the most water in 2 min.) wins! Wait until I say water in 2 min.) wins! Wait until I say “GO”“GO”

• What properties of water are exhibited? What properties of water are exhibited? how?how?

Intermolecular forces

Hydrogen Bond Stronger bond between molecules with H and F, O, N

link

Meniscus and MORE!

Why is there a meniscus?Is there always a meniscus?

What is the mathematical relationship between diameter and meniscus?

VERNIER VERNIER CALIPERS CALIPERS measure measure

inside inside diameter diameter

(ID).(ID).

1.1. set span in between the set span in between the upper jaws, dial to snug upper jaws, dial to snug fit.fit.

2.2. Read the first whole Read the first whole number in cmnumber in cm

3.3. The tenths place is where The tenths place is where the first line passes. (letter the first line passes. (letter A) A)

4.4. The hundredths place is The hundredths place is where the lines match. where the lines match. (letter B)(letter B)

1.19cm1.19cm