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Chapter 8 Pages 8-2 to 8-5
The Water Planet
The Water Planet
8-2
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Chapter 8 Pages 8-2 to 8-5
The Water Planet
The Water Planet
 Water covers about 71% of the Earth’s surface.
Considering the depth and volume, the world’s ocean
provides more than 99% of the biosphere – the
habitable space on Earth.
 The vast majority of water on
Earth can’t be used directly for
drinking, irrigation, or industry
because it’s salt water.
8-3
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The Water Planet
Chapter 8 Pages 8-2 to 8-5
The Water Planet
 As the population increases, so does the need for
water.
 Part of the solution to meeting this demand lies in
understanding what water is, where it goes,
and how it cycles through nature.
8-4
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The Water Planet
Chapter 8 Pages 8-2 to 8-5
The Water Planet
 The Hydrologic Cycle.
8-5
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Chapter 8 Pages 8-2 to 8-5
The Water Planet
The Water Planet
 The ocean is vast.
 Considering depth and volume, the world’s ocean
provides more than 99% of the biosphere - the
habitable space on Earth.
 The entire ocean is a biosphere
- organisms live everywhere
in the water column.
 How does this compare to
land animals?
8-6
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Chapter 8 Pages 8-2 to 8-5
The Water Planet
The Water Planet
 Our ocean on planet Earth averages 3,730 meters
(12,238 feet) deep and it contains more than 1.18
trillion cubic kilometers (285 million cubic miles) of
water.
 The deepest known point
in any ocean is the
Challenger Deep in
the Mariana Trench.
8-7
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Chapter 8 Pages 8-5 to 8-8
Water’s Unique Properties
Water’s Unique Properties
8-8
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Chapter 8 Pages 8-5 to 8-6
Water’s Unique Properties
The Polar Molecule
 Molecules are the simplest part of a substance.
 Compared to many important
molecules, water is a simple
molecule - it’s chemical
symbol = H2O.
 Consists of three atoms - two
hydrogen and one oxygen.
 The way it’s held together
gives it unique properties.
8-9
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Chapter 8 Pages 8-5 to 8-6
Water’s Unique Properties
The Polar Molecule
 Covalent bonding.
 Covalent bonds result in the
formation of molecules.
 The hydrogen atoms bond
to the oxygen atoms with a
covalent bond.
 A covalent bond is formed by
atoms sharing electrons. This
makes water a very stable
molecule. In water, the oxygen
atom shares the electrons of two single-electron
hydrogen atoms.
8 - 10
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Chapter 8 Pages 8-5 to 8-6
Water’s Unique Properties
The Polar Molecule
 A molecule with positive and negative charged
ends has polarity and is called a polar molecule.
 Water is a polar molecule.
 The two hydrogen atoms
have a net excess positive
charge.
 The oxygen atom has a
net excess negative charge.
8 - 11
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Chapter 8 Pages 8-5 to 8-6
Water’s Unique Properties
The Polar Molecule
 The water molecule’s polarity allows it to bond
with adjacent water molecules.
 The positively charged
hydrogen end of one water
molecule attracts the
negatively charged oxygen
end of another water molecule.
 This bond between water
molecules is called a
hydrogen bond.
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 Hydrogen bonds.
 Individual hydrogen bonds are
weak compared to covalent
bonds - only 6% as strong.
 Hydrogen bonds can easily
break and reform.
Chapter 8 Pages 8-5 to 8-6
Water’s Unique Properties
The Polar Molecule
8 - 13
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Chapter 8 Pages 8-6 to 8-8
Water’s Unique Properties
The Effects of Hydrogen Bonds
 Being a polar molecule, water has these
characteristics:
 Liquid Water. The most important characteristics
of the hydrogen bonds is the ability to make water
a liquid at room temperature.
Without them, water would be a gas - water
vapor or steam at room temperature.
Hydrogen bonds hold the molecules together,
requiring more energy (heat) to form steam.
8 - 14
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Chapter 8 Pages 8-6 to 8-8
Water’s Unique Properties
The Effects of Hydrogen Bonds
 Being a polar molecule, water has these
characteristics:
 Cohesion/Adhesion. Because hydrogen bonds
attract water molecules to each other, they tend to
stick together. This is cohesion. Water also sticks
to other materials due to its polar nature. This is
adhesion.
 Example of adhesion - a raindrop clinging to the
surface of a leaf.
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Chapter 8 Pages 8-6 to 8-8
Water’s Unique Properties
The Effects of Hydrogen Bonds
 Being a polar molecule, water has these
characteristics:
 Viscosity. This is the tendency for a fluid (gas or
liquid) to resist flow.
 Most fluids change viscosity as temperatures
change.
 The colder water gets, the more viscous it
becomes. It takes more energy for organisms to
move through it, and drifting organisms use less
energy to keep from sinking.
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The Effects of Hydrogen Bonds
Chapter 8 Pages 8-6 to 8-8
Water’s Unique Properties
 Being a polar molecule, water has these
characteristics:
 Surface Tension. A skin-like surface formed due
to the polar nature of water. Surface tension is
water’s resistance to objects attempting to
penetrate its surface.
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The Effects of Hydrogen Bonds
Chapter 8 Pages 8-6 to 8-8
Water’s Unique Properties
 Being a polar molecule, water has these
characteristics:
 Ice Floats: as water cools enough to turn from a
liquid into solid ice, the hydrogen bonds spread
the molecules into a crystal structure that takes up
more space than liquid water, so it floats.
8 - 18
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Chapter 8 Pages 8-6 to 8-8
Water’s Unique Properties
The Effects of Hydrogen Bonds
 If ice sank, the ocean would be entirely frozen –
or at least substantially cooler – because water
would not be able to retain as much heat.
 The Earth’s climate would be colder – perhaps too
cold for life.
 So, the question is… “How
important is Hydrogen Bonds
to your very existence?”
8 - 19
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Chapter 8 Pages 8-9 to 8-23
The Inorganic Chemistry of Water
The Inorganic
Chemistry of Water
8 - 20
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Chapter 8 Pages 8-9 to 8-11
The Inorganic Chemistry of Water
Solutions and Mixtures in Water
 A solution occurs when the molecules of one
substance are evenly dispersed among the
molecules of another substance.
 Water can act as a solvent. (often called the
“universal solvent”)
 A solvent is the more abundant substance in a
solution; usually a liquid.
 A solute is the substance being dissolved and is less
abundant in the solution. Solutes are usually a solid
or gas.
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Solutions and Mixtures in Water
Chapter 8 Pages 8-9 to 8-11
The Inorganic Chemistry of Water
 A mixture is the combination of two or more
substances that are not chemically bonded, and not
in fixed proportions to each other.
 Two kinds of mixtures: Homogeneous and
Heterogeneous.
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Solutions and Mixtures in Water
 Colloid - a homogeneous solution with intermediate
particle size between a solution and suspension. Like
milk.
Chapter 8 Pages 8-9 to 8-11
The Inorganic Chemistry of Water
 Two kinds of mixtures:
 Homogeneous - has a uniform appearance
throughout. Examples: Milk, fog, sugar and water,
smoke, and stirred up dust in the air.
 Heterogeneous - is not uniform throughout and
consists of visibly different substances. Examples:
India ink, oil and water, sand and water.
 Suspension - a heterogeneous mixture of larger, visible
particles that will settle out on standing. Like sand and
water.
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 Water can be part of both homogeneous and
heterogeneous mixtures.
 Water’s polar nature makes it good solvent.
 Regarding salt, let’s examine why water is a good
solvent.
Chapter 8 Pages 8-9 to 8-11
The Inorganic Chemistry of Water
Solutions and Mixtures in Water
Salt crystals are held
together by ionic bonding.
Sodium loses an electron,
making it positive. Chlorine
gains and electron making it
negative. The opposites
attract forming salt.
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 Water dissolves salt.
 Water’s charged ends pull apart - dissociate - the
salt (sodium chloride - NaCl) crystal.
 Sodium and chlorine become charged particles ions.
Chapter 8 Pages 8-9 to 8-11
The Inorganic Chemistry of Water
Solutions and Mixtures in Water
Salt - sodium chloride - NaCl
in its crystal or solid state.
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 Water dissolves salt.
 The positive sodium ion is attracted to the
negative oxygen side of the water molecule.
 The negative chlorine ion is attracted to the
positive hydrogen
side of the
water molecule.
Chapter 8 Pages 8-9 to 8-11
The Inorganic Chemistry of Water
Solutions and Mixtures in Water
8 - 26
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 Salinity refers to sodium chloride and many other
salts dissolved in seawater.
 Salinity includes the total quantity of all dissolved
inorganic solids in seawater (ions).
 Dissolved salts includes sodium chloride and
everything else.
 Scientist’s measure salinity in various ways – current
method uses how well water conducts electricity.
Chapter 8 Pages 8-11 to 8-12
The Inorganic Chemistry of Water
Salts and Salinity
8 - 27
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Chapter 8 Pages 8-11 to 8-12
The Inorganic Chemistry of Water
Salts and Salinity
 Salinity is expressed in parts per thousand (‰).
 The ocean’s average salinity is 35, meaning 35‰ or
35g/kg.
 Variations as small as 0.01 are of importance to
oceanographers.
 The ocean’s salinity varies from near zero at river
mouths to more than 40‰ in confined, arid regions.
 The proportion of the different dissolved salts
never change, only the relative amount of water.
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 Colligative properties are properties of a liquid
that may be altered by the presence of a solute
and are associated primarily with seawater.
 Pure water doesn’t have colligative properties.
Fresh water, with some solutes, can have
colligative properties to some degree.
 The strength of the colligative properties depends
on the quantity of solute.
Chapter 8 Page 8-13
The Inorganic Chemistry of Water
The Colligative Properties of Seawater
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 The colligative properties of seawater include:
 Raised boiling point. Seawater boils at a higher
temperature than pure fresh water.
 Decreased freezing temperature. As salinity
increases, water resists freezing (why salt is put
on a road during ice/snow storms).
Chapter 8 Page 8-13
The Inorganic Chemistry of Water
The Colligative Properties of Seawater
8 - 30
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The Colligative Properties of Seawater
Chapter 8 Page 8-13
The Inorganic Chemistry of Water
 The colligative properties of seawater include:
 Ability to create osmotic pressure. Liquids flow
or diffuse from areas of high concentration to
areas of low concentration until the concentration
equalizes.
Osmosis occurs when this
happens through a
semi-permeable membrane,
such as a cell wall.
Because it contains dissolved
salts, water in seawater
exists in lower concentration
than in fresh water.
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 The colligative properties of seawater include:
 Electrically conductive. Ability to conduct an
electrical current. A solution that can do this is
called an electrolyte.
 Decreased heat capacity. Takes less heat to
raise the temperature of seawater.
 Slowed evaporation. Seawater evaporates more
slowly than fresh due to the attraction between
ions and water molecules.
Chapter 8 Page 8-13
The Inorganic Chemistry of Water
The Colligative Properties of Seawater
8 - 32
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Chapter 8 Page 6-14
The Inorganic Chemistry of Water
The Principle of Constant Proportions
 In seawater no matter how much the salinity varies,
the proportions of several key inorganic elements and
compounds do not change. Only the amount of water
and salinity changes.
 This constant relationship of proportions in
seawater is called the principle of constant
proportions.
 This principle does not apply to everything
dissolved in seawater – only the dissolved salts.
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Dissolved Solids in Seawater
Chapter 8 Page 8-14
The Inorganic Chemistry of Water
 Next to hydrogen and oxygen, chloride and
sodium are the most abundant chemicals in
seawater.
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 If you know how much you have of any one seawater
chemical, you can figure out the salinity using the
principle of constant proportions.
 Chloride accounts for 55.04% of dissolved solids –
determining a sample’s chlorinity is relatively easy.
 The formula for determining salinity is based on the
chloride compounds:
Chapter 8 Pages 8-14 to 8-16
The Inorganic Chemistry of Water
Determining Salinity, Temperature,
and Depth
salinity ‰ = 1.80655 x chlorinity ‰
Sample of seawater is tested at 19.2‰ chlorinity:
salinity ‰ = 1.80655 x 19.2‰
salinity ‰ = 34.68‰
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Determining Salinity, Temperature,
and Depth
Chapter 8 Pages 8-14 to 8-16
The Inorganic Chemistry of Water
 Most commonly, salinity is determined with a salinometer.
It determines the electrical conductivity of the water.
 An important tool to measure the properties of seawater are the
Argo floats - an array of 3,000 free-drifting floats.
Salinometer
Argo Float
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Determining Salinity, Temperature,
and Depth
Chapter 8 Pages 8-14 to 8-16
The Inorganic Chemistry of Water
 Another tool is the conductivity, temperature, and depth (CTD)
sensor. The CTD profiles temperature and salinity with depth.
 Another less accurate way to determine salinity is with a
refractometer.
CTD
Sensor
Refractometer
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Chapter 8 Pages 8-16 to 8-18
The Inorganic Chemistry of Water
Why the Seas Are Salty
 A source of sea salts appears to be minerals and chemicals
eroding and dissolving into fresh water flowing into the
ocean.
 Waves and surf contribute by eroding coastal rock.
 Hydrothermal vents change
seawater by adding some
materials while removing others.
 Scientists think these
processes all counterbalance
so the average salinity of
seawater remains constant.
 The ocean is said to be in
chemical equilibrium.
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 Most of the ocean surface has average salinity, about
35‰. Waves, tides, and currents mix waters to make
them more uniform.
 Precipitation and evaporation have opposite effects
on salinity.
Chapter 8 Pages 8-18 to 8-19
The Inorganic Chemistry of Water
Salinity, Temperature, and Water Density




Rainfall decreases salinity by adding fresh water.
Evaporation increases salinity by removing fresh water.
Freshwater input from rivers lowers salinity.
Abundant river input and low evaporation results in salinities
well below average.
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Salinity, Temperature, and Water Density
Chapter 8 Pages 8-18 to 8-19
The Inorganic Chemistry of Water
 Salinity and temperature also vary with depth.
 Density differences causes water to separate into
layers.
 High-density water lies beneath low-density water.
8 - 40
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Salinity, Temperature, and Water Density
Chapter 8 Pages 8-18 to 8-19
The Inorganic Chemistry of Water
 Water’s density is the result of its temperature
and salinity characteristics:
 Low temperature and high salinity are features of highdensity water.
 Relatively warm, low-density surface waters are separated
from cool, high-density deep waters by the thermocline, the
zone in which temperature changes rapidly with depth.
 Salinity differences overlap temperature differences and the
transition from low-salinity surface waters to high-salinity
deep waters is known as the halocline.
 The thermocline and halocline together make the
pycnocline, the zone in which density increases with
increasing depth.
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Chapter 8 Pages 8-18 to 8-19
The Inorganic Chemistry of Water
Salinity, Temperature, and Water Density
Global Salinity
8 - 42
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 pH measures acidity or alkalinity.
 Seawater is affected by solutes. The relative
concentration of positively charged hydrogen
ions and negatively charged hydroxyl ions
determines the water’s acidity or alkalinity.
 It can be written like this:
Chapter 8 Pages 8-20 to 8-22
The Inorganic Chemistry of Water
Acidity and Alkalinity
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 Acidic solutions have a lot of hydrogen ions (H+), it is
considered an acid with a pH value of 0 to less
than 7.
 Solutions that have a lot of hydroxyl ions (OH-) are
considered alkaline. They are also called basic
solutions. The pH is higher than 7, with anything over
9 considered a concentrated alkaline solution.
Chapter 8 Pages 8-20 to 8-22
The Inorganic Chemistry of Water
Acidity and Alkalinity
8 - 44
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The Inorganic Chemistry of Water
Chapter 8 Pages 8-20 to 8-22
Acidity and Alkalinity
8 - 45
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Acidity and Alkalinity
The Inorganic Chemistry of Water
pH can be measured chemically or electronically.
Pure water has a pH of 7 - neutral pH.
Seawater pH ranges from 7.8 to 8.3 - mildly alkaline.
Ocean’s pH remains relatively stable due to buffering.
 A buffer is a substance that reduces the tendency
of a solution to become too acidic or alkaline.
 Seawater is buffered primarily by carbon dioxide.
Chapter 8 Pages 8-20 to 8-22




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 Seawater is fairly stable, but pH changes with
depth because the amount of carbon dioxide
tends to vary with depth.
 Shallow depths have less carbon dioxide
with a pH around 8.5.
 Shallow depths have the greatest density of
photosynthetic organisms which use the carbon
dioxide, making the water slightly less acidic.
Chapter 8 Pages 8-20 to 8-22
The Inorganic Chemistry of Water
Acidity and Alkalinity
8 - 47
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 Middle depths have more carbon dioxide and
the water is slightly more acidic with a lower pH.
 More carbon dioxide present from the respiration
of marine animals and other organisms, which
makes water somewhat more acidic with a lower
pH.
Chapter 8 Pages 8-20 to 8-22
The Inorganic Chemistry of Water
Acidity and Alkalinity
8 - 48
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The Inorganic Chemistry of Water
Chapter 8 Pages 8-20 to 8-22
Acidity and Alkalinity
 Deep water is more acidic with no photosynthesis
to remove the carbon dioxide.
 At this depth there is less organic activity, which
results in a decrease in respiration and carbon
dioxide. Mid-level seawater tends to be more
alkaline.
 At 3,000 meters (9,843 feet) and deeper, the water
becomes more acidic again.
 This is because the decay of sinking organic
material produces carbon dioxide, and there are
no photosynthetic organisms to remove it.
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The variation of
pH and total
dissolved
inorganic carbon
with depth.
Chapter 8 Pages 8-20 to 8-22
The Inorganic Chemistry of Water
Acidity and Alkalinity
8 - 50
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Chapter 8 Pages 8-23 to 8-30
The Organic Chemistry of Water
The Organic Chemistry
of Water
8 - 51
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Chapter 8 Pages 8-23 to 8-24
The Organic Chemistry of Water
Biogeochemical Cycles
 Organic chemistry deals mainly with chemical
compounds consisting primarily of carbon and
hydrogen.
 Inorganic compounds such as dissolved sea salts
account for the majority of dissolved solids in
seawater.
 Dissolved organic elements also interact with
organisms on a significant scale.
 These elements are crucial to life and differ from
the sea salts in several ways.
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Chapter 8 Pages 8-23 to 8-24
The Organic Chemistry of Water
Biogeochemical Cycles
 Proportions of organic elements in seawater
differ from the proportions of sea salts because:
 The principle of constant proportions does not
apply to these elements.
 These nonconservative constituents have
concentrations and proportions that vary
independently of salinity due to biological and
geological activity.
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Biogeochemical Cycles
Chapter 8 Pages 8-23 to 8-24
The Organic Chemistry of Water
 All life depends on material from the nonliving part of
the Earth.
 The continuous flow of elements and compounds
between organisms (biological form) and the Earth
(geological form) is the biogeochemical cycle.
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Biogeochemical Cycles
Chapter 8 Pages 8-23 to 8-24
The Organic Chemistry of Water
 Organisms require specific elements and compounds
to stay alive.
 Aside from gases used in respiration or
photosynthesis, those substances required for life
are called nutrients.
 The primary nutrient elements related to seawater
chemistry are carbon, nitrogen, phosphorus, silicon, iron,
and a few other trace metals.
 Not all elements and compounds cycle at the same rate.
 The biogeochemical cycle of the various nutrients affects
the nature of organisms and where they live in the sea.
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Chapter 8 Pages 8-24 to 8-26
The Organic Chemistry of Water
Carbon
 Carbon is the fundamental element of life.
 Carbon compounds form the basis for chemical
energy and for building tissues.
 The seas have plenty of carbon in several forms. It
comes from:
 Carbon dioxide in the air.
 Natural mineral sources - such as carbonate
rocks.
 Organisms - excretion and decomposition.
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 Carbon cycle.
The movement of
carbon between
the biosphere
and the nonliving
world is described
by the carbon cycle.
Chapter 8 Pages 8-24 to 8-26
The Organic Chemistry of Water
Carbon
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 Nitrogen is another element crucial to life on Earth.
 Organisms require nitrogen for organic
compounds such as protein, chlorophyll, and
nucleic acids.
 Nitrogen makes up about 78% of the air and 48% of
the gases dissolved in seawater.
Chapter 8 Pages 8-26 to 6-27
The Organic Chemistry of Water
Nitrogen
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 Gaseous nitrogen must be converted to a chemically
usable form before it can be used by living
organisms.
 Bacteria “fixes” nitrogen from the air into usable
compounds - nitrate, nitrite and ammonium.
 In these forms, autotrophs take up the nitrogen and
incorporate it into their systems as protein.
Chapter 8 Pages 8-26 to 6-27
The Organic Chemistry of Water
Nitrogen
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 The nitrogen cycle.
Bacteria and humans
carry out many of the
important steps of the
nitrogen cycle.
The cycle has four
stages: Assimilation,
Decomposition,
Nitrification,
Denitrification.
Chapter 8 Pages 8-26 to 6-27
The Organic Chemistry of Water
Nitrogen
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 Phosphorus is another element important to life
because it is used in the ADP/ATP cycle, by which
cells convert chemical energy into the energy
required for life.
 Phosphorus combined with calcium carbonate is a
primary component of bones and teeth.
Chapter 8 Page 8-28
The Organic Chemistry of Water
Phosphorus and Silicon
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 The phosphorus cycle.
Dissolved phosphorous is
carried to the sea by
runoff and leaching from
land. Phosphorus is used
by plants, then recycled
through animals until it is
released from waste
and decay.
Chapter 8 Page 8-28
The Organic Chemistry of Water
Phosphorus and Silicon
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Phosphorus and Silicon
The Organic Chemistry of Water
Chapter 8 Page 8-28
 Silicon is used similarly by some organisms
in the marine environment (including diatoms
and radiolarians) for their shells and skeletons.
 Silicon exists in these organisms
as silicon dioxide, called silica.
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Chapter 8 Page 8-29
The Organic Chemistry of Water
Iron and Trace Metals
 Iron and other trace metals fit into the definition of a
micronutrient.
 Micronutrients are substances essential to
organisms in very small amounts.
 These are essential to organisms for
constructing specialized proteins, including
hemoglobin and enzymes. Plants need iron to
produce chlorophyll.
 Other trace metals used in enzymes include
manganese, copper, and zinc.
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Chapter 8 Pages 8-30 to 8-34
The Organic Chemistry of Water
Chemical Factors that
Affect Marine Life
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Diffusion and Osmosis
Chapter 8 Pages 8-30 to 8-32
Chemical Factors That Affect Marine Life
 Diffusion is the tendency for a liquid, gas, or solute to
flow from an area of high concentration to an area of
low concentration.
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Diffusion and Osmosis
Chapter 8 Pages 8-30 to 8-32
Chemical Factors That Affect Marine Life
 Osmosis is diffusion through a semipermeable
cell membrane.
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Diffusion and Osmosis
Chapter 8 Pages 8-30 to 8-32
Chemical Factors That Affect Marine Life
 This has important implications with respect to
marine animals.
 Hypertonic - having a higher salt concentration,
and the water will diffuse into the cells. What happens
when you put a marine fish into fresh water.
 Isotonic - when water concentration inside the cell
is the same as the surrounding water outside the
cell. There is no osmotic pressure in either direction. Marine
fish cells are isotonic.
 Hypotonic - having a lower salt concentration than the
surrounding water. It is what happens when you put a
freshwater fish into seawater.
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Diffusion and Osmosis
Isotonic
Chapter 8 Pages 8-30 to 8-32
Chemical Factors That Affect Marine Life
Hypertonic
Hypotonic
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 Osmosis through a semipermeable cell
membrane is called passive transport.
 Passive transport moves materials in and out of a
cell by normal diffusion.
Chapter 8 Pages 8-32 to 8-34
Chemical Factors That Affect Marine Life
Active Transport, Osmoregulators,
and Osmoconformers
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 The process of cells moving materials from low
to high concentration is called active transport.
 Active transport takes energy because
it goes against the flow of diffusion.
Chapter 8 Pages 8-32 to 8-34
Chemical Factors That Affect Marine Life
Active Transport, Osmoregulators,
and Osmoconformers
8 - 71
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 Marine fish that have a regulation process that
allows them to use
active transport to adjust
water concentration
within their cells
are osmoregulators.
Chapter 8 Pages 8-32 to 8-34
Chemical Factors That Affect Marine Life
Active Transport, Osmoregulators, and
Osmoconformers
8 - 72
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Active Transport, Osmoregulators, and
Osmoconformers
Chapter 8 Pages 8-32 to 8-34
Chemical Factors That Affect Marine Life
 Marine organisms that have their internal salinity rise
and fall along with the water salinity are
osmoconformers.
8 - 73
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