PHYSICAL PROPERTIES OF
SEAWATER
YOU NEED YOUR TEXT
BOOKS TODAY
JQ: Jot a list of anything you
know about water.
How Unique is Water?
• Water is one of only 3 naturally occurring
liquids (mercury and ammonia) on Earth
• Only substance occurring naturally that
exists in all 3 states – solid, liquid, and gas
– on Earth’s surface
• Extremely large liquid range (0oC - 100oC)
• Expands, becomes less dense as a solid
The Nature of Pure Water
• Water made of 2 hydrogen atoms and 1
oxygen atom
• Water is a polar molecule (+ end & – end)
• Water’s unusual structure causes them to
“stick together”
• Water molecules form hydrogen bonds
• Hydrogen bonds not very strong, but make
water different from any other substance
on Earth
JQ: What feature of water is ultimately
responsible for giving water its unique physical
.
What physical feature of water
is ultimately responsible for
giving water its unique physical
properties? Explain.
Water is a polar molecule – it
has a positive and negative end
Figure 3.1
Hydrogen Bond – attraction
between positive end of one water
molecule and the negative end of
another
Water has…
• Cohesion – sticks to
itself
• Adhesion – sticks to
others
• Surface Tension – a
measure of how
difficult it is to stretch
or break the surface
of water
– No waves without
surface tension
Water has…
• Low Viscosity – little resistance to flow
• Good for Earth’s marine organisms –
WHY?
The Three States of Water
• Water is the only substance that naturally occurs
as a solid, liquid and gas on Earth
• Evaporation absorbs heat
• Condensation releases heat
Water is Weird
• Density – the mass of a certain volume of
a substance
• Solid water is less dense than liquid water
• Water becomes more dense as it cools
– Water is most dense @ 4º C
– Becomes less dense as it nears 0º C
• Good for the planet – WHY?
Heat Capacity
• The amount of heat required to raise the temperature of
1 gram of a substance 1º C
– Water has one of the highest
– 1 calorie raises 1 gram of water 1º C
– It absorbs large amounts of energy before the
temperature changes
• Good for earth’s climate – WHY?
Mohave Desert
Point Pleasant
JQ: Again…What feature of water is ultimately
responsible for giving water its unique physical
.
Why is Water Important?
• Water is the universal solvent
• Water can dissolve more than any
other natural substance
• Water can dissolve many hydrophilic
substances
– Ionic compounds
– Other polar compounds
• http://programs.northlandcollege.edu/biology
/Biology1111/animations/dissolve.html
Figure 3.5
Seawater has dissolved solids…
• Source –
– Chemical weathering of crustal rocks
– Hydrothermal vents
– From volcanic eruptions
Exploring the Density of Water
Lab
• Review your notes – What is unique about
water’s density as solid/liquid?
• At what temperature is water densest?
JQ: What is a hydrometer?
How does it work?
Density…
• Pure Water less dense than salt water
• Warmer water less dense than colder
water
• Denser near poles or equator?
YOU NEED YOUR OCEANOGRAPHY
TEXT BOOK TODAY!
Density…
• Density increases as you go deeper
• Ocean is layered, stratified
• Seen in profiles of salinity, temperature,
and density
• The greater the difference in density
between surface and deep water, the
more stable the water column and the
harder it is to mix vertically
Figure 3.31
Pressure…
• Water is noncompressible – does not
change volume with increasing pressure
• Pressure increases with increasing depth
– 1 atm (14.7 lbs/in2) for every 10 m (33 ft)
– Pressure in deepest trench ~1100 atm
– As pressure increases, gases are
compressed (remember “The Bends”?)
Figure 3.13
Buoyancy
• The ability of an object to float by
displacing a volume of water equal to its
own weight
Water…
• Transmits energy
– Heat
– Light
– Sound
• Refraction – the bending of light and
sound waves due to density differences
that affect the speed of energy
transmission
– The denser the water, the greater the
refraction
Link
• Archer fish – evolved to account for
refraction in order to hunt
Water is …
• Transparent –
transmits light energy
readily
– Important for
photosynthesis
– Oceans are blue
because blue light
penetrates the
deepest
– Coastal waters
sometimes green
because blue
absorbed
Water…
• Transmits sound faster & farther than in air
– 1500 m/s in seawater (& 60 times farther)
– 334 m/s in air
• At 1000 m combination of salinity, temp &
pressure creates a zone of minimum
velocity for sound – the Sofar Layer
(sound fixing and ranging layer)
– Sound waves produced here do not escape
& travel long distances
Sofar Channel