Transcript power point

►The Water Planet
►Water’s Unique Properties
►The Inorganic Chemistry of Water
►The Organic Chemistry of Water
►Chemical Factors That Affect Marine Life
The Water Planet
Water covers about 71% of the Earth’s
surface. Considering the depth and volume,
the world’s oceans provide 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.
As the population increases,
so does the need for water.
The Water Cycle
Part of the
solution to
meeting this
demand lies in
understanding
what water is,
where it goes,
and how it
cycles through
nature.
The Polar Molecule
Water is a simple
molecule; the way it’s
held together gives it
unique properties.
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.
A molecule
with positive
and negative
charged ends
has polarity
and is called
a 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.
The Effects of Hydrogen Bonds
Being a polar molecule, water has
these 4 characteristics:
1.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.
Characteristics of water, continued
2. 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.
3. Viscosity. This is the tendency for a fluid to
resist flow.
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.
4. 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.
Surface Tension
Penny Lab
Bubble-ology Lab
The Effects of Hydrogen Bonds (continued)
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.
If ice sank, the oceans 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.
Solutions and Mixtures in Water
A solution occurs when the molecules of one
substance are homogeneously dispersed among the
molecules of another substance.
A mixture occurs when two or more substances
closely intermingle, yet retain their individuality.
Salts and Salinity
Salinity includes the total quantity of all dissolved
inorganic solids in seawater.
Sodium chloride (rock salt or halite) is the most
common and abundant sea salt.
Scientist’s measure salinity in various ways –
expressed in parts per thousand (‰).
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.
The Colligative Properties of Seawater
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 colligative properties of seawater include:
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.
Raised boiling point. Seawater boils at a
higher temperature than pure fresh water.
Decreased freezing temperature. Seawater
freezes at a lower temperature than fresh
water due to increased salinity.
(The colligative properties of seawater, continued:)
Slowed evaporation. Seawater evaporates more
slowly than fresh due to the attraction between
ions and water molecules.
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
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.
Dissolved Solids in Seawater
Next to hydrogen and oxygen, chloride and
sodium are the most abundant chemicals in
seawater.
Determining Salinity, Temperature, and Depth
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:
salinity ‰ = 1.80655 x chlorinity ‰
Sample of seawater is tested at 19.2‰
chlorinity:
salinity ‰ = 1.80655 x 19.2‰
salinity ‰ = 34.68‰
Most commonly,
salinity is determined
with a salinometer.
This device
determines chlorinity
and calculates the
salinity based on the
water’s electrical
conductivity. It is
accurate.
The primary tool to
measure the
properties of
seawater 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.
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 appear to contribute by
eroding coastal rock.
Hydrothermal vents change seawater by
adding some materials while removing others.
Scientists believe these processes
all counterbalance so the average
salinity of seawater remains
constant.
The ocean is said to be in chemical
equilibrium.
Salinity, Temperature, and Water Density
Although the ocean’s average salinity is about
35‰, it isn’t uniform.
Precipitation and evaporation have opposite effects
on salinity.
 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.
Salinity and temperature also
vary with depth.
Density differences causes water
to separate into layers.
High-density water lies beneath
low-density water.
Water’s density is the result of its temperature and
salinity characteristics:
 Low temperature and high salinity are features of
high-density 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.
Salinity, Temperature, and Water Density (continued)
Acidity and Alkalinity
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:
Acidic solutions have a lot of hydrogen ions, it is
considered an acid with a pH value of 0 to less
than 7.
Solutions that have a lot of hydroxyl ions are
considered alkaline. They are also called basic
solutions. The pH is higher than 7, with anything
over 9 considered a concentrated alkaline solution.
Acidity and Alkalinity
(continued)
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.
 This depth has greatest density of photosynthetic organisms
which use the carbon dioxide, making the water slightly less
acidic.
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.
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.
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 owing to
biological and geological activity.
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.
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 nutrients 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.
Carbon
Carbon is the fundamental element of life.
Carbon compounds form the basis for
chemical energy and for building tissues.
Carbon dioxide must be transformed
into other carbon compounds for use
by heterotrophs.
The
movement
of carbon
between the
biosphere
and the
nonliving
world is
described
by the
carbon
cycle.
Nitrogen
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.
Phosphorus and Silicon
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 is a necessary component of DNA
 Phosphorus combined with calcium carbonate is a
primary component of bones and teeth.
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.
Iron and Trace Metals
Iron and other trace metals fit into
the definition of a micronutrient.
These are essential to organisms for
constructing specialized proteins,
including hemoglobin and enzymes.
Other trace metals used in enzymes
include manganese, copper, and zinc.
Diffusion and Osmosis
Diffusion is the tendency for a liquid,
gas, or solute to flow from an area of
high concentration to an area of low
concentration.
Osmosis is diffusion through a
semipermeable cell membrane.
This has important implications
with respect to marine animals.
Hypertonic cells - having a higher
salt concentration, and the water
will diffuse into the cells.
It is 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 cells - having a lower salt
concentration than the surrounding
water.
It is what happens when you put a
freshwater fish into seawater.
Active Transport, Osmoregulators, and
Osmoconformers
Osmosis through a semipermeable cell
membrane is called passive transport.
Passive transport moves materials in and
out of a cell by normal diffusion.
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.
Marine fish that
have a regulation
process that
allows them to use
active transport
to adjust water
concentration
within their cells
are
osmoregulators.
Marine organisms that have their
internal salinity rise and fall along
with the water salinity are
osmoconformers.
Ex. - jellyfish
Mediterranean Sea and its surroundings
6 - 54
Seas & Countries that border the Mediterranean Sea
6 - 55
Strong currents enter from the Atlantic and the Black Sea
6 - 56
Diagram of explanation
In summary
In arid climates, evaporation from the sea
surface greatly exceeds precipitation &
runoff
This “high salinity” water sinks.
Part of this deep, dense water eventually
flows out of the Mediterranean Sea over the
shallow sill at Gibraltar & down into the
Atlantic
The currents at Gibraltar can be compared to
2 large rivers flowing in opposite directions,
one over the other
Although the Black Sea does not add to
the density of the Mediterranean Sea,
its large excess of precipitation and
river runoff adds to the volume of the
Mediterranean Sea.
The dilute surface waters form a
shallow, low density layer that does
flow into the Mediterranean Sea
through the Bosporus.
Review of Density – ions separate
(egg lab principles)
Egg lab explanation
6 - 61
Unit 4
►The Physics of Water
►How Water Physics Affect Marine Life
The Physics
of Water
Seawater’s chemical properties affect how
life functions in the oceans. Water’s physical
properties not only affect life processes of
marine organisms, but of human beings in the
water.
Heat and Heat Capacity
Heat is the kinetic energy in the
random movement, or vibration, of
individual atoms and molecules in a
substance.
The faster molecules move, the
more heat there is. Total heat
energy is measured based on both
the quantity and speed of
vibrating molecules.
Temperature measures
only how fast the
molecules vibrate.
The two most common
temperature systems
are Fahrenheit and
Celsius. Celsius is most
used in science
because it is based on
water’s physical
properties.
Heat capacity of a substance is the
amount of heat energy required to
raise a given amount of a substance
by a given temperature.
 Scientists express heat capacity
in terms of the amount of heat
energy it takes to change one
gram of a substance by 1°C.
 It’s expressed as the number of
calories required.
 It takes more heat energy to
raise water’s temperature than
that of most substances.
 Therefore water can absorb
or release a lot of heat with
little temperature change.
Water’s heat
capacity affects
the world’s climate
and weather.
Heat is carried
to areas that
would otherwise
be cooler, and
heat is absorbed
in areas that
would otherwise
be hotter.
Water Temperature and Density
As water cools it becomes denser. At 3.98°C (39.16°F) it
reaches maximum density. Below this point, it crystallizes into
ice. As water moves into a solid state* it becomes less dense.
Ice does not form all at once at the freezing point of 0°C
(32°F), but crystallizes continuously until all liquid turns solid.
Temperature does not drop any further until all the liquid
water freezes, even though heat continues to leave.
 This produces non-sensible heat – a change in heat energy
that cannot be sensed with a thermometer.
 The non-sensible heat lost when water goes from liquid to
solid state is called the latent heat of fusion.
 Sensible heat is that which you can sense with a
thermometer.
* State is an expression of a substance’s form as it changes
from solid, to liquid, to gas with the addition of heat.
Temperature and density of water
(maximum density of water)
Latent Heat of Vaporization
Latent heat of vaporization is the heat
required to vaporize a substance.
It takes more latent heat to vaporize
water than to freeze it because when
water freezes only some of the
hydrogen bonds break.
When it vaporizes, all the hydrogen
bonds must break, which requires more
energy.
Thermal Inertia
The tendency of water to resist temperature
change is called thermal inertia.
Thermal equilibrium means water cools at about
the same rate as it heats.
These concepts are important to life and Earth’s
climate because:
 Seawater acts as a global thermostat,
preventing broad temperature swings.
Temperature changes would be drastic
between night and day and between summer
and winter.
Without the thermal inertia, many –
perhaps most – of the organisms on
Earth could not survive the drastic
temperature changes that would
occur each night.
Ocean Water Density
Seawater
density varies
with salinity
and
temperature.
 This causes
seawater to
stratify, or
form layers.
Dense water is heavy and sinks below less dense
layers. The three commonly found density layers are:
1. Surface zone – varies in places from absent to 500 meters
(1,640 feet). In general it extends from the top to about 100
meters (328 feet). This zone accounts for about only 2% of the
ocean’s volume.
2. Thermocline – separates the surface zone from the deep
zone. It only needs a temperature or salinity difference to
exist. This zone makes up about 18% of the ocean’s volume.
3. Mid-water & Deep zone – lies below the thermocline. It is
a very stable region of cold water beginning deeper than 1,000
meters (3,280 feet) in the middle latitudes, but is shallower in
the polar regions. The deep zone makes up about 80% of the
ocean’s volume.(be prepared to draw out a diagram of these
layers on the test – see page 7-14 in your textbook)
Light
Water scatters and absorbs light. When light reaches the water’s
surface, some light penetrates, but, depending on the sun’s angle,
much may simply reflect back out of the water.
 Within the water, light reflects off light-colored suspended
particles.
 Dark colored suspended particles and algae absorb some of
the light.
 Water molecules absorb the energy, converting light into heat.
 Water absorbs colors at the red end of the spectrum more
easily than at the blue end.
Two zones exist with respect to light
penetration:
 1. Photic Zone – where light reaches (can be as deep
as 200 meters (656 feet). The photic zone has two
subzones.
Euphotic Zone – the upper shallow portion where
most biological production occurs – comprises
about 1% of the oceans.
Dysphotic Zone – where light reaches, but not
enough for photosynthetic life.
 2. Aphotic Zone – it makes up the vast majority of
the oceans. Where light does not reach and only a
fraction of marine organisms live.
Temperature
Compared to land-based climates, marine organisms
live in a much less challenging environment with
respect to temperature range.
 Ectotherm – An organism who's internal
temperature changes with seawater temperature.
Commonly called “cold-blooded.”
 Endotherm – Organisms that have an internal
temperature that varies, but remains 9°-16°C
(48.2°- 60.8°F) warmer than the surrounding
water.
 Homeotherm – Have an internal temperature that
is relatively stable. They are called “warmblooded”; marine mammals and birds are in this
category.
Temperature affects metabolism – the higher
the temperature within an organism the more
energy-releasing chemical processes
(metabolism) happen.
Endotherms and homeotherms can tolerate a
wide range of external temperatures.
Internal heat regulation allows endotherms an
advantage.
Their metabolic rate remains the same
regardless of external temperature
allowing them to live in a variety of
habitats.
Sound
Sound travels five times faster
in water than in air.
 It travels through warm water
faster than cool…but it travels
faster in deep water due to
pressure.
 Sound bounces off suspended
particles, water layers, the
bottom and other obstacles.
 Sound travels much farther
through water than light does.
 Sound is eventually absorbed
by water as heat.
Because sound travels so well in water,
marine mammals use echolocation to sense
an object’s size, distance, density, and
position underwater.
Pressure
Pressure exerted by water is called
hydrostatic pressure.
It’s simply the weight of the water.
 At 10 meters (33 feet) hydrostatic
pressure is equal to atmospheric
pressure – 1 bar/ata.
 At 10 meters (33 feet) the total
pressure is 2 bar – 1 bar from
atmospheric pressure plus 1 bar
from hydrostatic pressure.
 A marine organism living at 10
meters (33 feet) experiences
twice the pressure present at sea
level. Pressure increases
1 bar for each additional 10 meters
(33 feet).
Hydrostatic pressure doesn’t affect
marine organisms because it is the same
inside the organism as outside.
Living tissue is made primarily of water,
which (within limits) transmits pressure
evenly. Since it’s in balance, pressure
doesn’t crush or harm marine
organisms.
Hydrostatic pressure is primarily an
issue only for organisms that have gas
spaces in their bodies.
Size and Volume
Using a sphere to substitute for a cell:
 The volume of a sphere increases with the cube
of its radius and the surface area increases
with the square of its radius.
If a cell were to increase diameter 24 times
original size, the volume would increase 64
times, but the surface area would increase only
16 times.
 High surface-to-volume ratio is important for
cell function. The bigger the cell, the lower the
surface-to-volume ratio, which means that there’s
less relative area through which to exchange
gases, nutrients, and waste.
This is why large organisms are multicellular
rather than a giant single cell.
Buoyancy
Archimedes’ Principle states that an object immersed
in a gas or liquid is buoyed up by a force equal to the
weight of the gas or liquid displaced.
 This means marine organisms don’t have to expend
much energy to offset their own weight
compared to a land-based existence.
It allows entire communities to exist simply by
drifting.
It allows organisms to grow larger than those on
land.
It allows many swimming creatures to live
without ever actually coming into contact with
the bottom.
(think about the blue whale – why would it be difficult for a landbased animal of the same size to exist?????)
Movement and Drag
Marine organisms avoid sinking by:
 Plumes, hairs, ribbons, spines, and
other protrusions that increase
their drag and help them resist
sinking.
 Others have buoyancy adaptations
that help them remain suspended in
the water column.
Some marine organisms need to
overcome drag as they swim.
Adaptations that help them overcome
drag:
 Moving or swimming very slowly.
 Excreting mucus or oil that actually
lubricates them to “slip” through the
water.
 The most common is to have a shape
that reduces drag – streamlining.
Currents
It is speculated that drifting provides
several advantages.
1. Drifting disperses organisms into new
habitats, ensuring survival should
something happen to the original
community.
2. May take organisms into nutrient-rich
areas, preventing too many
offspring from competing for the same
resources in the original community.