Intro to Biology and Basic
Chemistry
Ch. 1,2,3
We are living in a golden age of biology
Biology is woven into the fabric of society as never
before
Knowledge of biologic...
 Biology is the scientific study of life
THE SCOPE OF BIOLOGY
Biology’s scope stretches across
the enormous diversity of ...
 Biologists explore life at levels ranging from the biosphere
to the molecules that make up cells
Figure 1.2.2
Cells Nucl...
The Unity of Life
Amoebas, molds, trees, and
people are all made from
similar cells
All organisms share a
common chemical...
 Diversity is the hallmark of life
Life in Its Diverse Forms
•The diversity of known life includes 1.7 million species
•E...
 Biodiversity can be both beautiful
and overwhelming
Grouping Species: The Basic Concept
Taxonomy is the
branch of biolog...
 The three domains of
life are
The Three Domains of Life
Bacteria
Archaea
Eukarya
Figure 1.8.1
Domain Bacteria Domain Arc...
 Bacteria and Archaea are both
prokaryotic domains
Figure 1.8.2
Domain Bacteria Domain Archaea
 Eukarya
includes at
least four
kingdoms
Protista
Plantae
Fungi
Animalia
Figure 1.8.3
Domain Eukarya
Kingdom Protista Kin...
Quick Think
 What are the 2 classifications of
prokaryotes?
 All eukaryotes belong to which group?
 Can you list the ch...
 Underlying the
diversity of life is a
striking unity, especially
at the lower levels of
structure
Unity in the Diversity...
 The universal architecture of eukaryotic cilia
Figure 1.9
(a) Paramecium (b) Cells from
fallopian
tube
(c) Cross section...
Think-Pair-Share
What is studied
under the scope of
biology?
 Think/Write 30 seconds
 Pair 1 minute
 Share with class ...
 The history of life
is a saga of a
restless Earth
billions of years
old
EVOLUTION:
BIOLOGY’S
UNIFYING THEME
Fossils docu...
 Life evolves
Each species is one twig of a branching tree of life
extending back in time
Figure 1.11
Giant
panda
Spectac...
 The evolutionary
view of life came into
focus in 1859 when
Charles Darwin
published The Origin
of Species
The Darwinian
...
 Darwin’s book developed two main points
Descent with modification
Natural selection
 Darwin was struck by the diversity of
animals on the Galápagos Islands
Natural Selection
He thought of adaptation to
the...
 Fourteen
species of
Galápagos
finches have
beak shapes
adapted to suit
their
environments
Medium
ground
finch
Cactus
gro...
 Darwin synthesized the concept of natural
selection from two observations that were
neither profound nor original
Darwin...
 Fact 1: Overproduction and struggle for existence
 Fact 2: Individual variation
The inescapable conclusion: Unequal rep...
 Natural selection
is the mechanism
of evolution
Figure 1.14
Population with varied inherited
traits
Elimination of indiv...
 Artificial selection is the selective breeding of domesticated
plants and animal by humans
Observing Artificial Selectio...
 There are many examples of natural
selection in action
Observing Natural Selection
The development of antibiotic-resista...
 Darwin’s publication of The Origin of Species fueled an
explosion in biological research
Evolution is one of
biology’s b...
Think-Pair-Share
How would you
explain
evolution and
natural selection
to someone
(briefly)?
Atoms & Molecules
The Chemistry of
Life
 Take any
biological
system apart
and you
eventually end
up at the
chemical level
Ecosystem
African...
Building Blocks of Matter
 Matter is the amount of
material in an object; it is
measured using mass (not
weight!)
Matter is composed of chemical
elements
 There are 92 naturally occuring
elements
 25 are essential to life
 Four of th...
Trace elements are also
essential for life
 Trace elements are
required for all
organisms in very
small amounts
 Iron is...
Atoms: smallest
unit of matter
that retains its
characteristics
-ex. H, C, Na
 Nucleus = protons
and neutrons
 Electrons...
The type of atom is determined
by the number of protons in its
nucleus.
Atomic Number
•the number of protons in the nucleu...
 Isotopes are alternate mass forms of an element
Isotopes
They have the same number of protons and electrons
But they hav...
 Radioactive isotopes
The nucleus decays, giving off particles and energy
Radioactive isotopes have many uses in research...
 Electrons determine how an
atom behaves when it
encounters other atoms
 The properties of an atom are
determined by the...
Stable Electron Configuration
The most stable electron
configuration is 8 in the outer
shell (2 for H and He)
All elements...
Electrons tend to exist at the lowest state
of potential energy - the lowest shell
 1st shell - holds
2 electrons max
 2...
Shell Relationships
Elements with the same number of
valence electrons tend to behave
similarly
 Atoms of the four elements most abundant in life
Figure 2.7
Electron
First
electron shell
(can hold
2 electrons)
Outermo...
Energy Emission
Energy may hit an electron and raise it to a higher level
This is an unstable condition
The electron emits...
Think-Pair-Share
What is an atom,
what are the parts
of an atom, and
which of these
parts is most
important to
reactivity...
Chemical Bonding and
Molecules
 Chemical reactions enable atoms to give up or
acquire electrons in order to complete thei...
 When an atom loses
or gains electrons, it
becomes electrically
charged
Ionic Bonds
Charged atoms are
called ions
Cations...
Opposites attract
Ionic Bonds
 Ionic bonds are formed
between oppositely
charged ions
 Ionic compounds are
salts
 Salts do not consist of...
 A covalent bond forms when two atoms share one or more
pairs of outer-shell electrons
Covalent Bonds
 Cells constantly rearrange molecules by breaking existing
chemical bonds and forming new ones
Chemical Reactions
Such ch...
 Chemical reactions can be symbolized with
equations
On the left side of
the equation are
the reactants, the
starting mat...
Balancing Equations
 Amount of matter on both sides of a chemical reaction
must stay the same
 Matter cannot be created ...
Molecules
 Formed from atoms that
“share” their electrons
(covalent bonding)
 Together they have a
neutral charge
 Ofte...
Inorganic Molecules
Organic Molecules
 Must include Carbon atom(s)
Organic Molecules
Think-Pair-Share
Why do we
say that
matter
cannot be
created or
destroyed?
Chemical Properties
of Water
Your Objective
Be able to state at least 1 property
of water that helps support life
AND
Be able to explain how the
chemic...
Water
and Life
 Life on Earth
began in
water and
evolved
there for 3
billion years.
 Modern life still remains tied
to w...
•Water is foundWater is found
as a liquid overas a liquid over
71% of the71% of the
earthearth
•The abundanceThe abundance...
 Studied in isolation, the water molecule is
deceptively simple
 Its two hydrogen atoms are joined to one
oxygen atom by...
 But the electrons of the covalent bonds are not
shared equally between oxygen and hydrogen
This unequal sharing makes wa...
 The polarity of
water results in
weak electrical
attractions
between
neighboring water
molecules
These
interactions
are ...
Polar Structure
Electronegativity of H20
Quick Think
 Why is a molecule
of water said to
have polar covalent
bonds?
 What kind of bonds
hold individual
water mol...
Water’s Life Supporting
Properties
 The polarity of water molecules and the
hydrogen bonding that results explain most
of...
 Water molecules
stick together as a
result of hydrogen
bonding
The Cohesion of Water
This is called
cohesion
Cohesion is...
Surface tension is the measure of how difficult
it is to stretch or break the surface of a liquid
Hydrogen
bonds give
wate...
Surface Tension
 Water drops are round because all the
molecules on the edge are pulled to the
middle.
Adhesion
 Water will also
adhere to other polar
substances
 This is called
adhesion
 It is due to the polar
nature of t...
Capillary Action
 Glass has polar
molecules.
 Glass can hydrogen
bond.
 Attracts the water
molecules.
 Some of the pul...
Meniscus
 Water curves up
along the side.
 This makes the
meniscus.
Quick Think
 How are adhesion and
cohesion similar and
different?
 Give an example of how
these properties help
support ...
Water moderates temperature
 Because of hydrogen bonding, water has
a strong resistance to temperature
change
Water moderates temperature
 Heat and temperature are related, but
different
 Heat is a measure of the amount of kinetic...
Water moderates temperature
 Water has a high specific heat
 Specific heat = the amount of heat that mustSpecific heat =...
Water moderates temperature
 Since water has a high specific heat, it
will not change temperature much when it
absorbs or...
Water moderates temperature
 So water can absorb
and store large
amounts of heat
while only changing
a few degrees in
tem...
Large bodies of water help to
moderate temperature
 Earth’s giant water supply
causes temperatures to stay
within limits ...
How water moderates
temperature
Water also has:Water also has:
High heat of fusionHigh heat of fusion
• The temp at which ...
 When water molecules get cold, they move
apart, forming ice
The Biological Significance of Ice
Floating
A chunk of ice h...
 The density of ice is lower than liquid water
 This is why ice floats
Figure 2.15
Hydrogen bond
Liquid water
Hydrogen b...
Change of State
Dipole Structure
 Ice floats in water because all ice
molecules are held in hexagons
 Center is open
space, making
ice 8...
 Since ice floats, ponds, lakes, and even the
oceans do not freeze solid
Marine life could not survive if bodies of water...
 Floating ice insulates water below,
preventing freezing: critical for ocean
animals
Maximum density: 3.98o
C
 Below this temp, form hexagonal polymers and
decrease density
 Above this, molecules are energ...
 A solution is a liquid consisting of two or
more substances evenly mixed
Water as the Solvent of Life
The dissolving age...
 When water is the
solvent, the result is
called an aqueous
solution
 Water is a good
solvent because it is
polar
 Ioni...
Solvent Properties
 Water dissolves salts by surrounding the atoms in the
salt molecule and neutralizing the ionic bond h...
Quick Think
What are some unique
properties of water that
allow it to support life and
how is this related to its
polar n...
Acids,
Bases &
Buffers
 Acid
Acids, Bases,
and pH
A chemical compound that donates H+
ions to solutions
Base
A compound that accepts H+
ions and...
Basic
solution
Neutral
solution
Acidic
solution
Oven cleaner
Household bleach
Household ammonia
Milk of magnesia
Seawater
...
pH scale (log scale)
Each number on the scale is 10x difference
from the number next to it
• pH 1 is 10x more acidic than ...
pH - Percent Hydronium
A measure of the percent of hydronium ions
in the solution
The greater the percent hydronium ions, ...
Measuring Acidity
 Buffers are substances that resist pH change
They accept H+
ions when they are in excess
They donate H+
ions when they a...
Buffers
 Dissolved CO2 in water acts as a buffer, a
substance that prevents large shifts in
pH.
Buffers help keep pool
an...
Buffer Systems
CO2 + H2O ←→ H2CO3 ←→ H+
+ HCO3
-
←→ H+
+ CO3
-2
H2CO3 is carbonic acid,
H+
is the hydronium ion
HCO3
-
is ...
Buffer Systems
CO2 + H2O ←→ H2CO3 ←→ H+
+ HCO3
-
←→H+
+ CO3
-2
 Adding CO2 shifts the reaction to the right and
produces ...
Buffer Systems
CO2 + H2O ←→ H2CO3 ←→ H+
+ HCO3
-
←→ H+
+ CO3
-2
 Removing CO2 shifts the reaction to the left,
combining ...
Ocean Buffers
AP Bio Ch. 1-3
AP Bio Ch. 1-3
AP Bio Ch. 1-3
AP Bio Ch. 1-3
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AP Bio Ch. 1-3

  1. 1. Intro to Biology and Basic Chemistry Ch. 1,2,3
  2. 2. We are living in a golden age of biology Biology is woven into the fabric of society as never before Knowledge of biological concepts is more important than ever
  3. 3.  Biology is the scientific study of life THE SCOPE OF BIOLOGY Biology’s scope stretches across the enormous diversity of life on Earth
  4. 4.  Biologists explore life at levels ranging from the biosphere to the molecules that make up cells Figure 1.2.2 Cells Nucleus within cell Cells in squirrel DNA
  5. 5. The Unity of Life Amoebas, molds, trees, and people are all made from similar cells All organisms share a common chemical language for their genetic material, DNA
  6. 6.  Diversity is the hallmark of life Life in Its Diverse Forms •The diversity of known life includes 1.7 million species •Estimates of the total diversity range from 5 million to over 30 million species
  7. 7.  Biodiversity can be both beautiful and overwhelming Grouping Species: The Basic Concept Taxonomy is the branch of biology that names and classifies species It formalizes the hierarchical ordering of organisms Figure 1.7
  8. 8.  The three domains of life are The Three Domains of Life Bacteria Archaea Eukarya Figure 1.8.1 Domain Bacteria Domain Archaea Domain Eukarya Kingdom Protista Kingdom Plantae Kingdom Fungi Kingdom Animalia
  9. 9.  Bacteria and Archaea are both prokaryotic domains Figure 1.8.2 Domain Bacteria Domain Archaea
  10. 10.  Eukarya includes at least four kingdoms Protista Plantae Fungi Animalia Figure 1.8.3 Domain Eukarya Kingdom Protista Kingdom Plantae Kingdom Fungi Kingdom Animalia
  11. 11. Quick Think  What are the 2 classifications of prokaryotes?  All eukaryotes belong to which group?  Can you list the characteristics of the prokaryotic domain Archaea?
  12. 12.  Underlying the diversity of life is a striking unity, especially at the lower levels of structure Unity in the Diversity of Life Example: the universal genetic language of DNA Evolution accounts for this combination of unity and diversity
  13. 13.  The universal architecture of eukaryotic cilia Figure 1.9 (a) Paramecium (b) Cells from fallopian tube (c) Cross section of cilium
  14. 14. Think-Pair-Share What is studied under the scope of biology?  Think/Write 30 seconds  Pair 1 minute  Share with class when asked to
  15. 15.  The history of life is a saga of a restless Earth billions of years old EVOLUTION: BIOLOGY’S UNIFYING THEME Fossils document this history Figure 1.10
  16. 16.  Life evolves Each species is one twig of a branching tree of life extending back in time Figure 1.11 Giant panda Spectacled bear Sloth bear Sun bear American black bear Asiatic black bear Polar bear Brown bear Ancestral bear
  17. 17.  The evolutionary view of life came into focus in 1859 when Charles Darwin published The Origin of Species The Darwinian View of Life Figure 1.12
  18. 18.  Darwin’s book developed two main points Descent with modification Natural selection
  19. 19.  Darwin was struck by the diversity of animals on the Galápagos Islands Natural Selection He thought of adaptation to the environment and the origin of new species as closely related processes As populations separated by a geographic barrier adapted to local environments, they became separate species
  20. 20.  Fourteen species of Galápagos finches have beak shapes adapted to suit their environments Medium ground finch Cactus ground finch Small tree finch Medium tree finch Woodpecker finch Large ground finch Small ground finch Large cactus ground finch Vegetarian finch Large tree finch Mangrove finch Green warbler finch Gray warbler finch Sharp-beaked ground finch Seed-eaters Cactus-flower -eaters Bud-eater Insect-eaters Ground finches Tree finches Warbler finches Common ancestor from South American mainland Figure 1.13
  21. 21.  Darwin synthesized the concept of natural selection from two observations that were neither profound nor original Darwin’s Inescapable Conclusion Others had the pieces of the puzzle, but Darwin could see how they fit together Darwin & Wallace
  22. 22.  Fact 1: Overproduction and struggle for existence  Fact 2: Individual variation The inescapable conclusion: Unequal reproductive success It is this unequal reproductive success that Darwin called natural selection The product of natural selection is adaptation
  23. 23.  Natural selection is the mechanism of evolution Figure 1.14 Population with varied inherited traits Elimination of individuals with certain traits Reproduction of survivors Increasing frequency of traits that enhance survival and reproductive success 1 2 3 4
  24. 24.  Artificial selection is the selective breeding of domesticated plants and animal by humans Observing Artificial Selection Figure 1.15
  25. 25.  There are many examples of natural selection in action Observing Natural Selection The development of antibiotic-resistant bacteria is one Figure 1.16
  26. 26.  Darwin’s publication of The Origin of Species fueled an explosion in biological research Evolution is one of biology’s best demonstrated, most comprehensive, and longest lasting theories Evolution is the unifying theme of biology
  27. 27. Think-Pair-Share How would you explain evolution and natural selection to someone (briefly)?
  28. 28. Atoms & Molecules
  29. 29. The Chemistry of Life  Take any biological system apart and you eventually end up at the chemical level Ecosystem African savanna Community All organisms in savanna Population Herd of zebrasOrganism Zebra Organ system Circulatory system Organ Heart Cell Heart muscle cell Tissue Heart muscle tissue Molecule DNA Atom Oxygen atom
  30. 30. Building Blocks of Matter  Matter is the amount of material in an object; it is measured using mass (not weight!)
  31. 31. Matter is composed of chemical elements  There are 92 naturally occuring elements  25 are essential to life  Four of these make up ~ 96% of the weight of the human body  Trace elements occur in smaller amounts
  32. 32. Trace elements are also essential for life  Trace elements are required for all organisms in very small amounts  Iron is essential to all organisms  Iodine is essential to vertebrates An iodine deficiency causes goiter
  33. 33. Atoms: smallest unit of matter that retains its characteristics -ex. H, C, Na  Nucleus = protons and neutrons  Electrons = in clouds around the nucleus, at varying energy levels
  34. 34. The type of atom is determined by the number of protons in its nucleus. Atomic Number •the number of protons in the nucleus What is the atomic number of carbon? Mass Number • the sum of the protons and neutrons What is the mass number of carbon? Atomic Elements
  35. 35.  Isotopes are alternate mass forms of an element Isotopes They have the same number of protons and electrons But they have a different number of neutrons Change in # of neutrons changes the mass number
  36. 36.  Radioactive isotopes The nucleus decays, giving off particles and energy Radioactive isotopes have many uses in research and medicine Example: PET scans
  37. 37.  Electrons determine how an atom behaves when it encounters other atoms  The properties of an atom are determined by the configuration of its outer electrons (aka valence electrons) Electron Arrangement and the Chemical Properties of Atoms
  38. 38. Stable Electron Configuration The most stable electron configuration is 8 in the outer shell (2 for H and He) All elements will try to gain, lose or share outer electrons in order to reach this configuration.
  39. 39. Electrons tend to exist at the lowest state of potential energy - the lowest shell  1st shell - holds 2 electrons max  2nd shell - holds up to 8 electrons  3rd shell - holds up to 8 electrons
  40. 40. Shell Relationships Elements with the same number of valence electrons tend to behave similarly
  41. 41.  Atoms of the four elements most abundant in life Figure 2.7 Electron First electron shell (can hold 2 electrons) Outermost electron shell (can hold 8 electrons) Carbon (C) Atomic number = 6 Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8 Hydrogen (H) Atomic number = 1
  42. 42. Energy Emission Energy may hit an electron and raise it to a higher level This is an unstable condition The electron emits energy as it drops down to original level
  43. 43. Think-Pair-Share What is an atom, what are the parts of an atom, and which of these parts is most important to reactivity and why?
  44. 44. Chemical Bonding and Molecules  Chemical reactions enable atoms to give up or acquire electrons in order to complete their outer shells  These interactions usually result in atoms staying close together  The atoms are held together by chemical bonds
  45. 45.  When an atom loses or gains electrons, it becomes electrically charged Ionic Bonds Charged atoms are called ions Cations - positive charge Anions - negative charge Sodium atom (Na) Chlorine atom (Cl) Complete outer shells Sodium ion (Na+ ) Chloride ion (Cl− ) Sodium chloride (NaCl)
  46. 46. Opposites attract
  47. 47. Ionic Bonds  Ionic bonds are formed between oppositely charged ions  Ionic compounds are salts  Salts do not consist of individual molecules • They are just an aggregate of cations and anions
  48. 48.  A covalent bond forms when two atoms share one or more pairs of outer-shell electrons Covalent Bonds
  49. 49.  Cells constantly rearrange molecules by breaking existing chemical bonds and forming new ones Chemical Reactions Such changes in the chemical composition of matter are called chemical reactions Hydrogen gas Oxygen gas Water Reactants Products
  50. 50.  Chemical reactions can be symbolized with equations On the left side of the equation are the reactants, the starting materials On the right side of the equation are the products, the end materials
  51. 51. Balancing Equations  Amount of matter on both sides of a chemical reaction must stay the same  Matter cannot be created or destroyed  Numbers (coefficients) are added in front of chemical formulas to BALANCE equations. 2NaOH + H2SO4 2H2O + Na2SO4
  52. 52. Molecules  Formed from atoms that “share” their electrons (covalent bonding)  Together they have a neutral charge  Often contain carbon and are then known as “organic” molecules  Can have single, double or triple bonding
  53. 53. Inorganic Molecules
  54. 54. Organic Molecules  Must include Carbon atom(s)
  55. 55. Organic Molecules
  56. 56. Think-Pair-Share Why do we say that matter cannot be created or destroyed?
  57. 57. Chemical Properties of Water
  58. 58. Your Objective Be able to state at least 1 property of water that helps support life AND Be able to explain how the chemical nature of water gives rise to that property
  59. 59. Water and Life  Life on Earth began in water and evolved there for 3 billion years.  Modern life still remains tied to water  Cells are composed of 70%- 95% water
  60. 60. •Water is foundWater is found as a liquid overas a liquid over 71% of the71% of the earthearth •The abundanceThe abundance of water is aof water is a major reasonmajor reason Earth isEarth is habitablehabitable
  61. 61.  Studied in isolation, the water molecule is deceptively simple  Its two hydrogen atoms are joined to one oxygen atom by single covalent bonds The structure of water H O H
  62. 62.  But the electrons of the covalent bonds are not shared equally between oxygen and hydrogen This unequal sharing makes water a polar molecule Oxygen is more electronegative than hydrogen, so it has a greater pull on the electrons (+) (+) (−) (−)
  63. 63.  The polarity of water results in weak electrical attractions between neighboring water molecules These interactions are called hydrogen bonds (b) (−) Hydrogen bond (+) (+) (−) (−) (+) (+) (−)
  64. 64. Polar Structure
  65. 65. Electronegativity of H20
  66. 66. Quick Think  Why is a molecule of water said to have polar covalent bonds?  What kind of bonds hold individual water molecules together?
  67. 67. Water’s Life Supporting Properties  The polarity of water molecules and the hydrogen bonding that results explain most of water’s life-supporting properties  Water’s cohesive nature  Water’s ability to moderate temperature  Floating ice  Versatility of water as a solvent
  68. 68.  Water molecules stick together as a result of hydrogen bonding The Cohesion of Water This is called cohesion Cohesion is vital for water transport in plants Microscopic tubes
  69. 69. Surface tension is the measure of how difficult it is to stretch or break the surface of a liquid Hydrogen bonds give water an unusually high surface tension Cohesion between water molecules form a skin-like surface Can support animals like “waterCan support animals like “water striders” in pondsstriders” in ponds
  70. 70. Surface Tension  Water drops are round because all the molecules on the edge are pulled to the middle.
  71. 71. Adhesion  Water will also adhere to other polar substances  This is called adhesion  It is due to the polar nature of the water molecule Caused by adhesion the water runs along the glass and does not fall straight.
  72. 72. Capillary Action  Glass has polar molecules.  Glass can hydrogen bond.  Attracts the water molecules.  Some of the pull is up.
  73. 73. Meniscus  Water curves up along the side.  This makes the meniscus.
  74. 74. Quick Think  How are adhesion and cohesion similar and different?  Give an example of how these properties help support life.
  75. 75. Water moderates temperature  Because of hydrogen bonding, water has a strong resistance to temperature change
  76. 76. Water moderates temperature  Heat and temperature are related, but different  Heat is a measure of the amount of kinetic energy in the atoms and molecules in something  Temperature measures the intensity of the heat  Whenever 2 objects meet, the cooler object absorbs heat from the warmer object until they are the same temperature
  77. 77. Water moderates temperature  Water has a high specific heat  Specific heat = the amount of heat that mustSpecific heat = the amount of heat that must be absorbed or lost to change thebe absorbed or lost to change the temperature of 1g of the substance 1° Ctemperature of 1g of the substance 1° C
  78. 78. Water moderates temperature  Since water has a high specific heat, it will not change temperature much when it absorbs or loses heat  This is because much of the absorbed heat is used to break hydrogen bonds, not increase the kinetic energy of the molecules
  79. 79. Water moderates temperature  So water can absorb and store large amounts of heat while only changing a few degrees in temperature
  80. 80. Large bodies of water help to moderate temperature  Earth’s giant water supply causes temperatures to stay within limits that permit life  Evaporative cooling removes heat from the Earth and from organisms
  81. 81. How water moderates temperature Water also has:Water also has: High heat of fusionHigh heat of fusion • The temp at which liquid turns solidThe temp at which liquid turns solid High heat of vaporizationHigh heat of vaporization • The temp at which liquid turns to gasThe temp at which liquid turns to gas
  82. 82.  When water molecules get cold, they move apart, forming ice The Biological Significance of Ice Floating A chunk of ice has fewer molecules than an equal volume of liquid water IceLiquid water
  83. 83.  The density of ice is lower than liquid water  This is why ice floats Figure 2.15 Hydrogen bond Liquid water Hydrogen bonds constantly break and re-form Ice Stable hydrogen bonds
  84. 84. Change of State
  85. 85. Dipole Structure  Ice floats in water because all ice molecules are held in hexagons  Center is open space, making ice 8% less dense than water.
  86. 86.  Since ice floats, ponds, lakes, and even the oceans do not freeze solid Marine life could not survive if bodies of water froze solid
  87. 87.  Floating ice insulates water below, preventing freezing: critical for ocean animals
  88. 88. Maximum density: 3.98o C  Below this temp, form hexagonal polymers and decrease density  Above this, molecules are energetic, water behaves like other liquids - expanding when warm and contracting when cool
  89. 89.  A solution is a liquid consisting of two or more substances evenly mixed Water as the Solvent of Life The dissolving agent is called the solvent The dissolved substance is called the solute Ion in solution Salt crystal
  90. 90.  When water is the solvent, the result is called an aqueous solution  Water is a good solvent because it is polar  Ionic (salts) and polar (sugars) compounds dissolve readily in water
  91. 91. Solvent Properties  Water dissolves salts by surrounding the atoms in the salt molecule and neutralizing the ionic bond holding the molecule together
  92. 92. Quick Think What are some unique properties of water that allow it to support life and how is this related to its polar nature?
  93. 93. Acids, Bases & Buffers
  94. 94.  Acid Acids, Bases, and pH A chemical compound that donates H+ ions to solutions Base A compound that accepts H+ ions and removes them from solution or a compound that dissociates in water to form hydroxide ions
  95. 95. Basic solution Neutral solution Acidic solution Oven cleaner Household bleach Household ammonia Milk of magnesia Seawater Human blood Pure water Urine Tomato juice Grapefruit juice Lemon juice; gastric juice pH scale To describe the acidity of a solution, we use the pH scale
  96. 96. pH scale (log scale) Each number on the scale is 10x difference from the number next to it • pH 1 is 10x more acidic than pH 2, 100x more acidic than pH 3, 1000x more acidic that pH 4, and so on
  97. 97. pH - Percent Hydronium A measure of the percent of hydronium ions in the solution The greater the percent hydronium ions, the more acidic the solution is HH22COCO33 -------------> H-------------> H++ ++ HCOHCO33 -- CARBONIC ACIDCARBONIC ACID HYDRONIUM BICARBONATEHYDRONIUM BICARBONATE IONION IONION
  98. 98. Measuring Acidity
  99. 99.  Buffers are substances that resist pH change They accept H+ ions when they are in excess They donate H+ ions when they are depleted Buffering is not foolproof Example: acid precipitation normal rain water (pH of 5-6) pH of acid rain is between 3-4
  100. 100. Buffers  Dissolved CO2 in water acts as a buffer, a substance that prevents large shifts in pH. Buffers help keep pool and spa water clean
  101. 101. Buffer Systems CO2 + H2O ←→ H2CO3 ←→ H+ + HCO3 - ←→ H+ + CO3 -2 H2CO3 is carbonic acid, H+ is the hydronium ion HCO3 - is the bicarbonate ion CO3 -2 is the carbonate ion
  102. 102. Buffer Systems CO2 + H2O ←→ H2CO3 ←→ H+ + HCO3 - ←→H+ + CO3 -2  Adding CO2 shifts the reaction to the right and produces more H+ ions making the water more acid.
  103. 103. Buffer Systems CO2 + H2O ←→ H2CO3 ←→ H+ + HCO3 - ←→ H+ + CO3 -2  Removing CO2 shifts the reaction to the left, combining H+ ions with carbonate and bicarbonate ions reducing the acidity.
  104. 104. Ocean Buffers

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