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PHYSICAL PROPERTIES OF SEAWATER

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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PHYSICAL PROPERTIES OF SEAWATER

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  1. PHYSICAL PROPERTIES OF SEAWATER

  2. 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

  3. 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

  4. Figure 3.1

  5. 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

  6. Water has… • Low Viscosity – little resistance to flow • Good for Earth’s marine organisms – WHY?

  7. 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

  8. 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?

  9. 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?

  10. 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

  11. 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

  12. 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

  13. Figure 3.5

  14. Seawater has dissolved solids… • Source – • Chemical weathering of crustal rocks • Hydrothermal vents • From volcanic eruptions

  15. 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

  16. 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

  17. Figure 3.31

  18. 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

  19. Figure 3.13

  20. Buoyancy • The ability of an object to float by displacing a volume of water equal to its own weight

  21. 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

  22. Water… • Transmits heat energy by • Conduction – molecule to molecule • Convection – moving fluids & density driven • Radiation – direct from source (sun)

  23. 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

  24. 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

  25. Sofar Channel

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