Seawater Chemistry JQ: If you add a pinch of salt to water, will it boil faster?

Salinity The total quantity (concentration) of dissolved inorganic solids in water About % by mass in oceans Average ~3.5% or 35 ppt (parts per thousand)

How do ions modify the physical properties of water? –Heat capacity decreases with increased salinity, but saltwater will boil at a higher temp IN other words, seawater will heat to 100 C more quickly, but not boil until 102 C So if you add a pinch of salt to water, will it boil faster? No.

How do ions modify the physical properties of water? –As salinity increases, the freezing point of water decreases Dissolved salts disrupt hydrogen bonding Sea ice forms at a lower temperature than freshwater ice *This is why we put Salt on icy driveway*

How do ions modify the physical properties of water? Seawater evaporates more slowly than fresh water –Dissolved salts attract water molecules (salt ions hold tighter to water than cohesion of water)

Major Constituents of Seawater at 34.4 ppt  Over 99% of seawater salinity comes from 6 ions:  Chloride55%  Sodium32%  Sulfate 8%  Magnesium 3%  Calcium 1%  Potassium 1%

Principle of Constant Proportions The percentage of salts in seawater is the same in samples from many places, regardless of how salty the water is –Same proportions for 33 ppt and 37 ppt

Dissolved Gases Seawater also contains dissolved gases Gases dissolve better in colder water (poles) -Nitrogen most 45% (dissolves from atmosphere) -Blue green algae convert Nitrogen into usable form for marine organisms (nitrogen fixation) 36% of dissolved gases – from atmosphere and photosynthesis - Carbon 15% - mostly from respiration and decomposition