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Salt Water

Salt Water. Properties of Salt Water. Salinity is the amount of dissolved salts in water The salinity of the oceans averages 35 ppt (parts per thousand) Fresh water averages 10 ppt

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Salt Water

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  1. Salt Water

  2. Properties of Salt Water • Salinity is the amount of dissolved salts in water • The salinity of the oceans averages 35 ppt (parts per thousand) • Fresh water averages 10 ppt • There are some variations in salinity due to differences in: the rates of evaporation, precipitation, and run-off

  3. Differences in Salinity • The salinity of the Red Sea is 41ppt and the salinity of the Dead Sea is nearly 300 ppt • Table salt (NaCl) accounts for 87% of the salinity of sea water • Sea water contains at least a trace amount of most elements found in the Earth’s crust

  4. Red Sea

  5. Dead Sea

  6. Salinity and Freezing • Salinity affects the freezing point of water • When ice forms in seawater the salt is extruded from the ice, leaving a more salty water beneath the ice. • Seawater therefore has no fixed freezing point

  7. Salinity and Density • Seawater is more dense than freshwater, so freshwater floats on seawater • An increase in salinity increases the density • A hydrometer is an instrument used to measure the buoyancy of a liquid by comparing its buoyancy to that of pure water

  8. It can be used to measure density • If the liquid is more dense than water, the hydrometer will float higher • If the liquid is less dense than water, they hydrometer will sink more

  9. Major constituents of seawater at 34.32% salinity: • Chloride ions • Sodium ions • Sulfate • Magnesium • Calcium • potassium • Bicarbonate • This is a chlorine atom

  10. Chloride and sodium give the ocean its salty taste • Molluscs use the calcium to make their shells • Crustaceans use calcium salts to build their bodies • Diatoms use silica to form their shells

  11. Snails secrete lead • Sponges remove iodine from the sea

  12. How salty is the ocean? • Maybe 50 million billion tons of dissolved solids • If the salt was removed, it would cover the Earth’s surface, 500ft thick • When 1 cubic foot of ocean water evaporates, it leaves 2.2 pounds of salt • When 1 cubic foot of Lake Michigan (fresh water) is evaporated, it leaves 0.01 pounds of salt • So, sea water is 200x saltier than fresh water

  13. Origin of the Sea • “ocean” and “sea” are used in the same context here • It is believed to be 500 million years old, based on fossil evidence • Scientists are unsure of what has formed the ocean, but believe that the atmosphere and the oceans have evolved over time from “degassing” of the Earth’s interior

  14. So, water vapour and other gases left the interior, went to form clouds • The Earth’s surface cooled • Rain began to fall for centuries • Rain drained into hollows in the Earth’s surface and formed an ocean • Gravity prevented it from leaving • Salts come from the breaking down of materials of the Earth’s crust

  15. Salt enters the sea from rivers and streams, and then is deposited on the ocean floor • The Sun’s heat vaporized pure water and leaves the salt behind

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