Warm up
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Transcript of Warm up
Warm upWarm up
1.1. What property of water allows a What property of water allows a water strider to water strider to ““walkwalk”” on water? on water?
2.2. Contrast Contrast adhesionadhesion and and cohesioncohesion. . Give an example of each.Give an example of each.
3.3. Contrast Contrast hydrophobichydrophobic and and hydrophilichydrophilic substances. Give an substances. Give an example of each.example of each.
You Must KnowYou Must Know
• The importance of hydrogen The importance of hydrogen bonding to the properties of water.bonding to the properties of water.
• Four unique properties of water, Four unique properties of water, and how each contributes to life on and how each contributes to life on Earth.Earth.
• How to interpret the pH scale.How to interpret the pH scale.• The importance of buffers in The importance of buffers in
biological systems.biological systems.
1. Polarity of H1. Polarity of H22OO
• OO-- will bond with H will bond with H++ on a different on a different molecule of Hmolecule of H22O = O = hydrogen bondhydrogen bond
• HH22O can form up to 4 bondsO can form up to 4 bonds
2. Properties of H2. Properties of H22OO
A.A. CohesionCohesion = H-bonding between = H-bonding between likelike molecules molecules
• Surface Tension Surface Tension = measure of how = measure of how difficult it is to break or stretch surface difficult it is to break or stretch surface of liquidof liquid
2. Properties of H2. Properties of H22OO
B.B. AdhesionAdhesion = bonding between = bonding between unlikeunlike molecules molecules
Adhesion of HAdhesion of H22O to vessel walls O to vessel walls counters ↓ pull of gravitycounters ↓ pull of gravity
2. Properties of H2. Properties of H22OO
C. C. TranspirationTranspiration = movement of H= movement of H22O O up plantsup plants
HH22OO clings to each other by clings to each other by
cohesioncohesion; cling to xylem tubes by ; cling to xylem tubes by adhesionadhesion
3. Moderation of 3. Moderation of temperaturetemperatureHeatHeat = Total amount of KE in system = Total amount of KE in system
TemperatureTemperature = measure intensity of = measure intensity of heatheat due to due to averageaverage KE of KE of moleculesmolecules
Which has higher temp?Which has higher temp?
More heat?More heat?
3. Moderation of 3. Moderation of temperaturetemperatureA.A. WaterWater’’s s high specific heathigh specific heat
• Change temp less when absorbs/loses Change temp less when absorbs/loses heatheat
• Large bodies of water absorb and store Large bodies of water absorb and store more heat more heat warmer coastal areas warmer coastal areas
• Create stable marine/land environmentCreate stable marine/land environment• Humans ~65% HHumans ~65% H22O O stable temp, stable temp,
resist temp. changeresist temp. change
3. Moderation of 3. Moderation of temperaturetemperatureB.B. Evaporative CoolingEvaporative Cooling
Water has high heat of vaporizationWater has high heat of vaporization Molecules with greatest KE leave as Molecules with greatest KE leave as
gasgas Stable temp in lakes & pondsStable temp in lakes & ponds Cool plantsCool plants Human sweatHuman sweat
3. Moderation of 3. Moderation of temperaturetemperatureC.C. Insulation by iceInsulation by ice – –
less dense, floating less dense, floating ice insulates liquid ice insulates liquid HH22O belowO below
Life exists under Life exists under frozen surface frozen surface (ponds, lakes, (ponds, lakes, oceans)oceans)
Ice = solid habitat Ice = solid habitat (polar bears)(polar bears)
4. Solvent of life4. Solvent of life
• SolutionSolution = liquid, homogeneous = liquid, homogeneous mixture of 2+ substancesmixture of 2+ substances
• SolventSolvent = dissolving agent = dissolving agent (liquid)(liquid)
• SoluteSolute = dissolved substance = dissolved substance• Water = versatile solventWater = versatile solvent
4. Solvent of life4. Solvent of life
• ““like dissolves likelike dissolves like””
Hydrophilic Hydrophobic
Affinity for H2O Repel H2O
Polar, ions Nonpolar
Cellulose, sugar, salt
Oils, lipids
Blood Cell membrane
5. Acids and Bases5. Acids and Bases
HH22O O H H++ + OH + OH--
(gains proton) H(gains proton) H++ + H + H22O O HH33OO++ ( (hydronium hydronium ionion))
(loses proton) H(loses proton) H22O – HO – H++ OHOH-- ((hydroxide ionhydroxide ion))
5. Acids and Bases5. Acids and Bases
• AcidAcid = increases H= increases H++ concentration concentration (HCl)(HCl)
• BaseBase = reduces H= reduces H++ concentration concentration (NaOH)(NaOH)
• Most biological fluids are pH 6-8Most biological fluids are pH 6-8
0 7 14
Basic
Acidic
pH Scale
Figure 3.10 The pH scale and pH values of some aqueous solutionsFigure 3.10 The pH scale and pH values of some aqueous solutions
Calculating pHCalculating pH
[H[H++][OH][OH--] = 10] = 10-14-14
n If [HIf [H++] = 10] = 10-6 -6 M, then [OHM, then [OH--] = 10] = 10-8-8
pH = -log [HpH = -log [H++]]1.1. If [HIf [H++] = 10] = 10-2-2
• -log 10-log 10-2 -2 = -(-2) = 2= -(-2) = 2• Therefore, pH = 2Therefore, pH = 2
2.2. If [OHIf [OH--] = 10] = 10-10-10
• [H[H++] = 10] = 10-4-4
• -log 10-log 10-4 -4 = -(-4) = 4= -(-4) = 4• Therefore, pH = 4Therefore, pH = 4
5. Acids and Bases5. Acids and Bases
BuffersBuffers: minimize changes in concentration : minimize changes in concentration of Hof H++ and OH and OH-- in a solution (weak acids in a solution (weak acids and bases)and bases)
• Buffers keep blood at pH ~7.4Buffers keep blood at pH ~7.4• If blood drops to 7 or up to 7.8, then deathIf blood drops to 7 or up to 7.8, then death
Carbonic Acid – Bicarbonate SystemCarbonic Acid – Bicarbonate System: : important buffers in blood plasmaimportant buffers in blood plasma
HH22COCO33 (carbonic acid) (carbonic acid) HCO HCO33-- (bicarbonate) + (bicarbonate) +
HH++
Ocean acidification threatens coral reef ecosystems
CO2 mixed with seawater Carbonic acid (lowers ocean pH)
H2O Property Chemical Explanation
Examples of Benefits to
Life
Cohesion•polar•H-bond•like-like
↑gravity plants, trees
Adhesion•H-bond•unlike-unlike
plants xylembloodveins
Surface Tension•diff. in stretch•break surface•H-bond
bugswater
Specific Heat•Absorbs & retains E•H-bond
oceanmod temp protect marine life
Evaporation•liquidgas•KE
CoolingHomeostasis
Universal Substance
•Polarityionic•H-bond
Good dissolversolvent