week 5 - physical and chemical properties of seawater Flashcards
properties of seawater (8 things)
- water
- temperature
- salinity
- density
- carbon dioxide
- acidity and alkalinity (pH)
- the carbonate buffer system
- chemical residence time
salinity and pH of seawater
salinity of 35 PSU and pH of 7.5 to 8.4
polarity
has a positive charge on one end of a molecule and negative charge on the other
- results in high latent heats of melting and vaporization
hydrogen bonds during heating (melting)
some break away from each other
hydrogen bonds in ice
lots of packed bonds
hydrogen bonds during vaporization (gas)
all of the bonds break
how is seawater different from regular water?
seawater has a high salinity
- proportion of ions is constant no matter where you get the water from
how to find total salinity
1.80555 x ionic abundance
what is temperature in relation to seawater
a measure of the amount of heat stored in the ocean
- affects density (the higher the temperature of the water, the lower the density)
- oceans store a lot of energy because of the high heat capacity
salinity
the salt content of seawater that is expressed in the concentration of ions in seawater
how does the salinity of seawater increase?
whenever pure water is removed by evaporation or the formation of ice
how does the salinity of seawater decrease?
when water is added by precipitation or the melting of ice
inorganic components in seawater
- chloride (CI-)
- sodium (NA+)
- sulfate (SO42)
- magnesium (MG2+)
- calclium (CA2+)
- potassium (K+)
factors that change the salinity of seawater
- evaporation of water and formation of ice increase salinity
- precipitation and ice melting (adding water) decreases salinity
with increasing salinity (3 things)
- density of water increases
- boiling point of water increases
- freezing point of water decreases
density in relation to seawater
- coldest waters are usually the most dense
- high density is favored by low temperature and high salinity
CO2 in relation to seawater
- highly soluble in seawater because it creates carbonic acid
dissolved organic carbon (DIC)
when carbonic acid dissociates to form hydrogen and bicarbonate ions, which then dissociates to form hydrogen and carbonate ions
- most of carbon dioxide in the oceans is stored in bicarbonate ions
acids
any compounds that when dissolved in water, releases hydrogen ions (H+, also called protons) which increases their concentration in solution
what makes pH neutral
when concentration of protons and hydrogen ions are equal in pure water
what happens when we dissolve acid in water?
the hydrogen ion concentration will increase as the acid dissociates
alkaline substance (base)
dissociates in water, releasing hydroxyl ions (OH-) into the solution
pH system
ranges from 0 to 14
- pure water has a neutral pH with a value of 7
- acidic solutions have extra H+ and has a value of LESS than 7
- alkaline (basic solutions) has pH values GREATER than 7
- when concentration goes down 1 level, the concentration goes up by ten
what happens when you add acid to water?
H reacts with bicarbonate and makes carbonic acid
what happens when you add alkaline to water?
OH- reacts with carbonic acid which makes bicarbonate
chemical residence time
the average length of time an element spends in the ocean between its addition and removal
amount of element in ocean/elements rate of removal (or addition from the ocean)