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PHYSICAL PROPERTIES OF SEAWATER. How Unique is Water?. Water is one of only 3 naturally occurring liquids (mercury and ammonia) Only substance occurring naturally that exists in all 3 states – solid , liquid, and gas – on Earth’s surface Extremely large liquid range (0 o C - 100 o C)

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how unique is water
How Unique is Water?
  • Water is one of only 3 naturally occurring liquids (mercury and ammonia)
  • 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
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
water has
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 has1
Water has…
  • Low Viscosity – little resistance to flow
  • Good for Earth’s marine organisms – WHY?
the three states of water
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
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
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?
changes of state
Changes of State
  • Latent Heat of Fusion / Melting –
    • The amount of heat required to melt a substance without change in temperature
    • 80 calories per gram
changes of state1
Changes of State
  • Latent Heat of Vaporization / Evaporation–
    • The amount of heat required to change a substance from a liquid to a gas without change in temperature
    • 540 calories per gram
why is water important
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
  • Form “spheres of hydration”
  • http://programs.northlandcollege.edu/biology/Biology1111/animations/dissolve.html
seawater has dissolved solids
Seawater has dissolved solids…
  • Source –
    • Chemical weathering of crustal rocks
    • Hydrothermal vents
    • From volcanic eruptions
water
Water …
  • Density of pure water is 1 g/mL @ 4º C
  • Density of seawater is 1.0278g/mL @ 4ºC
  • Density is determined by temperature and salinity
    • Seawater gets denser as it gets saltier, colder or both
  • Because temperature varies more than salinity, density is controlled by temperature
density
Density…
  • Changes with depth
  • Densest water sinks
  • Ocean becomes 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
pressure
Pressure…
  • Water is noncompressible– does not change volume with increasing pressure
  • So is seawater
  • Pressure increases with increasing depth
    • Has small effect on volume
    • 1 atm (14.7 lbs/in2) for every 10 m (33 ft)
    • Pressure in deepest trench ~1100 atm
    • As pressure increases, gases are compressed
buoyancy
Buoyancy
  • The ability of an object to float by displacing a volume of water equal to its own weight
water1
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
    • increases with increasing salt, decreases with increasing temperature
water2
Water…
  • Transmits heat energy by
    • Conduction – molecule to molecule
    • Convection – moving fluids & density driven
    • Radiation – direct from source (sun)
water is
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
water3
Water…
  • Transmits soundfaster & 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
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