Salt WaterSalt Water

Properties of Salt WaterProperties of Salt Water

Salinity is the amount of dissolved salts in Salinity is the amount of dissolved salts in waterwater

The salinity of the oceans averages 35 ppt The salinity of the oceans averages 35 ppt (parts per thousand)(parts per thousand)

Fresh water averages 10 pptFresh water averages 10 ppt There are some variations in salinity due There are some variations in salinity due

to differences in: the rates of evaporation, to differences in: the rates of evaporation, precipitation, and run-offprecipitation, and run-off

Differences in SalinityDifferences in Salinity

The salinity of the Red Sea is 41ppt and The salinity of the Red Sea is 41ppt and the salinity of the Dead Sea is nearly 300 the salinity of the Dead Sea is nearly 300 pptppt

Table salt (NaCl) accounts for 87% of the Table salt (NaCl) accounts for 87% of the salinity of sea watersalinity of sea water

Sea water contains at least a trace amount Sea water contains at least a trace amount of most elements found in the Earth’s crustof most elements found in the Earth’s crust

Red SeaRed Sea

Dead SeaDead Sea

Salinity and FreezingSalinity and Freezing

Salinity affects the freezing point of waterSalinity affects the freezing point of water When ice forms in seawater the salt is When ice forms in seawater the salt is

extruded from the ice, leaving a more salty extruded from the ice, leaving a more salty water beneath the ice. water beneath the ice.

Seawater therefore has no fixed freezing Seawater therefore has no fixed freezing pointpoint

Salinity and DensitySalinity and Density

Seawater is more dense Seawater is more dense than freshwater, so than freshwater, so freshwater floats on freshwater floats on seawaterseawater

An increase in salinity An increase in salinity increases the densityincreases the density

A hydrometer is an A hydrometer is an instrument used to instrument used to measure the buoyancy of measure the buoyancy of a liquid by comparing its a liquid by comparing its buoyancy to that of pure buoyancy to that of pure waterwater

It can be used to measure densityIt can be used to measure density If the liquid is more dense than water, the If the liquid is more dense than water, the

hydrometer will float higherhydrometer will float higher If the liquid is less dense than water, they If the liquid is less dense than water, they

hydrometer will sink morehydrometer will sink more

Major constituents of Major constituents of seawater at 34.32% seawater at 34.32% salinity:salinity:

Chloride ionsChloride ions Sodium ionsSodium ions SulfateSulfate MagnesiumMagnesium CalciumCalcium potassiumpotassium BicarbonateBicarbonate

This is a chlorine atomThis is a chlorine atom

Chloride and sodium give Chloride and sodium give the ocean its salty tastethe ocean its salty taste

Molluscs use the calcium Molluscs use the calcium to make their shellsto make their shells

Crustaceans use calcium Crustaceans use calcium salts to build their bodiessalts to build their bodies

Diatoms use silica to form Diatoms use silica to form their shellstheir shells

Snails secrete leadSnails secrete lead Sponges remove Sponges remove

iodine from the seaiodine from the sea

How salty is the ocean?How salty is the ocean?

Maybe 50 million billion tons of dissolved solidsMaybe 50 million billion tons of dissolved solids If the salt was removed, it would cover the If the salt was removed, it would cover the

Earth’s surface, 500ft thickEarth’s surface, 500ft thick When 1 cubic foot of ocean water evaporates, it When 1 cubic foot of ocean water evaporates, it

leaves 2.2 pounds of saltleaves 2.2 pounds of salt When 1 cubic foot of Lake Michigan (fresh When 1 cubic foot of Lake Michigan (fresh

water) is evaporated, it leaves 0.01 pounds of water) is evaporated, it leaves 0.01 pounds of saltsalt

So, sea water is 200x saltier than fresh waterSo, sea water is 200x saltier than fresh water

Origin of the SeaOrigin of the Sea

““ocean” and “sea” are ocean” and “sea” are used in the same context used in the same context herehere

It is believed to be 500 It is believed to be 500 million years old, based million years old, based on fossil evidenceon fossil evidence

Scientists are unsure of what Scientists are unsure of what has formed the ocean, but has formed the ocean, but believe that the atmosphere believe that the atmosphere and the oceans have evolved and the oceans have evolved over time from “degassing” of over time from “degassing” of the Earth’s interiorthe Earth’s interior

So, water vapour and other gases left So, water vapour and other gases left the interior, went to form cloudsthe interior, went to form clouds

The Earth’s surface cooledThe Earth’s surface cooled Rain began to fall for centuriesRain began to fall for centuries Rain drained into hollows in the Rain drained into hollows in the

Earth’s surface and formed an oceanEarth’s surface and formed an ocean Gravity prevented it from leavingGravity prevented it from leaving Salts come from the breaking down of Salts come from the breaking down of

materials of the Earth’s crustmaterials of the Earth’s crust

Salt enters the sea Salt enters the sea from rivers and from rivers and streams, and then is streams, and then is deposited on the deposited on the ocean floorocean floor

The Sun’s heat The Sun’s heat vaporized pure water vaporized pure water and leaves the salt and leaves the salt behindbehind