The Oceans Heat Capacity and Salinity

Water is the solvent.  NaCl (salt) is the solute.

     Water has a high HEAT CAPACITY.  Heat capacity is the amount of heat needed to raise the temperature of 1 gram of a substance by 1 degree Celsius.  Water's specific heat is 4.186 joule/gram*C.  Because of water's high heat capacity, marine organisms do not experience sudden swings in temperature that may occur on land.  Water's hydrogen bonds makes it an excellent SOLVENT.  A solvent is a substance, usually a liquid, capable of dissolving another substance.  Water can dissolve more things than any other natural substance.
     The oceans contain enough salt to cover the entire planet with a layer more than 500 feet thick!  The salts in sea water comes from the chemical weathering of rocks and the OUT-GASSING of hydrothermal vents.  Out-gassing is the release of adsorbed or occluded gasses or water vapor, usually by heating.  The amount of a solid materical dissolved in water is a measure of it's SALINITY.  The salinity of sea water is typically 3.5%, or more commonly, salinity is referred to as "parts per thousand" (3.5%=35%o).  A salinity of 3.5% indicates that sea water contains 96.5% pure water and 3.5% SOLUTES.  A solute is the substance that is dissolved in a solution.  Only 6 ions (Chlorine Cl-, Sodium Na+, Magnesium Mg2+, Calcium Ca2+, Potassium K+, and Sulfate SO42-)compose 99% of the solids dissolved in sea water, and of these Sodium (Na+) and Chloride (Cl-) account for 85%.  Salinity also influences the density of sea water; the saltier the water the denser it is.  The density of sea water therefore depends on it's salinity and it's temperature. 

Next lecture I will discuss dissolved gasses in sea water.