Should we control a chemical that:

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Should we control a chemical that

• Causes excessive sweating and vomiting.
• Is a major component in acid rain.
• Can cause severe burns in its gaseous state.

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• Accidental inhalation can kill you.
• Contributes to erosion.
• Decreases the effectiveness of car brakes.
• Has been found in tumors of terminal cancer
  patients.

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What is the chemical?

• Dihydrogen monoxide
• Otherwise known as H2O

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Chapter 3Water and the Fitness of the Environment
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Question?

• What molecule Is the most common In living Cells?
• Water - most cells are 70 - 95
  
  water.

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The Water Planet
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Properties Of Water

• Be ready and able to discuss several of the
  following properties.
• Focus on definitions and examples.
• Review water structure and H-bonds from
  Chapter 2.

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Liquid Water Is Cohesive

• Water sticks to water.
• Why?
• Because the polarity of water results in
  hydrogen bonding.

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Liquid Water is Adhesive

• Water sticks to other molecules.
• Why?
• Hydrogen bonding.

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Water transport in trees uses Cohesion and
Adhesion
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Water Has A High Surface Tension

• The surface of water is difficult to stretch or
  break.
• Why? Hydrogen bonding.

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Water Has A High Specific Heat

• Specific Heat - the amount of heat needed to
  raise 1 g of the substance 1 degree C.
• Why?
• Hydrogen bonding.

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Heat

• Total quantity of kinetic energy due to molecular
  motion.

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Temperature

• Measures the average speed of the molecules.

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Celsius Scale

• Will be used for most of our temperature
  measurements.
• O oC - water freezes
• 100 oC - water boils
• 37 oC - human body
  

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Water Stabilizes Temperature

• Water can absorb and store a huge amount of heat
  from the sun.
• Result - climate moderation
• Result - organisms are able to survive
  temperature changes.

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Fig. 3-5
San Bernardino 100
Burbank 90
Santa Barbara 73
Riverside 96
Los Angeles (Airport) 75
Santa Ana 84
Palm Springs 106
70s (F)
80s
Pacific Ocean
90s
100s
San Diego 72
40 miles
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Water Has A High Heat Of Vaporization

• Heat of Vaporization the quantity of
  heat a liquid must absorb for 1g of it to convert
  to a gaseous state.

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Evaporative Cooling
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Result

• Water cools organisms from excessive heat
  buildup.
• Why?
• Hydrogen bonding

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Water Expands When It Freezes

• The distance between water molecules INCREASES
  from the liquid to the solid form.
• Why?
• Hydrogen bonding

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Solids and Liquids
Water
Benzene
Floats
Sinks
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States of Matter
Liquid
Gas
Solid
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Result

• Aquatic life can live under ice.

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Water Is A Versatile Solvent

• Water will form a solution with many materials.
• Why?
• Hydrogen bonding

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Solution

• Homogeneous mixture of two or more substances.

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Solvent

• The dissolving agent.
• The material in the greater quantity.

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Solute

• The substance that is dissolved.
• The material in the lesser quantity.

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Hydrophilic Materials

• Materials that dissolve in water.
• Hydro - water
• philic - to like or love
• Have ionic or polar regions (polar covalent
  bonds) on their molecules for H bonds.

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Hydrophobic

• Materials that repel water.
• Hydro - water
• phobic - to fear
• Have non-polar covalent bonds. Ex - lipids.

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Without Water Life Would Not Be Possible!!
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Solution Concentration

• Usually based on Molarity.
• Molarity - the number of moles of solute per
  liter of solution.

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Moles

• The molecular weight of a substance in grams.
• One Avogadros number of molecules.
• 6.02 X 1023

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One Mole of each
Sugar
Copper Sulfate
Sulfur
Mercury Oxide
Sodium Chloride
Copper
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Comment

• AP Biology students should be able to calculate
  solutions in Molarity.

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Dissociation of Water

• Water can sometimes split into two ions.
• In pure water the concentration of each ion is
  10-7 M

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• Adding certain solutes disrupts the balance
  between the two ions.
• The two ions are very reactive and can
  drastically affect a cell.

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Acids

• Materials that can release H
• Example HCl
• HCl H Cl-

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Acid Rain
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Acid Rain
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Bases

• Materials that can absorb H
• Often reduce H by producing OH-
• Example NaOH
• NaOH Na OH-

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Neutrals

• Materials that are neither acids nor bases.

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Candice - IA
AP Biology
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Homework

• Read chapter 3, 4
• Lab - Macromolecules
• Chapter 3 Wed. 8/27
• Chapter 4 Fri. 8/29

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pH Scale

• A logarithmic scale for showing H concentration
• pH - log H

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pH Scale
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Example

• For a neutral solution
• H is 10-7
• or - log 10-7
• or - (-7)
• or 7

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• Acids pH lt7 etc.
• Bases pH gt7 etc.
• Each pH unit is a 10x change in H

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Comment

• H OH- 14
• Therefore, if you know the concentration of one
  ion, you can easily calculate the other.

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Fig. 3-9
pH Scale
0
1
Battery acid
Gastric juice, lemon juice
2
H
H
H
Vinegar, beer, wine, cola
OH
H
3
H
OH
Increasingly Acidic H gt OH
H
H
H
4
Tomato juice
Acidic solution
Black coffee
5
Rainwater
6
Urine
OH
Saliva
OH
Neutral H OH
7
Pure water
OH
H
H
OH
OH
Human blood, tears
H
H
H
8
Seawater
Neutral solution
9
10
Increasingly Basic H lt OH
Milk of magnesia
OH
OH
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OH
OH
H
Household ammonia
OH
OH
OH
H
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Basic solution
Household bleach
13
Oven cleaner
14
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Buffers

• Materials that have both acid and base
  properties.
• Resist pH shifts.
• Cells and other biological solutions often
  contain buffers to prevent damage.

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Summary

• Be able to discuss the properties of water.
• Be able to measure solution concentrations in
  Molarity.
• Be able to work pH scale questions.