10.2 How Ocean Water Differs from Fresh Water Ocean water’s salinity = 200X greater than fresh water Average salinity of oceans is 35 parts per thousand Oceans at equator (evaporation) and poles (ice) have the highest salinity (removing water increases salinity) Ocean locations near rivers have low salinity, due to addition of fresh water See page 368 - 370 from the World Ocean Atlas 2001 (c) McGraw Hill Ryerson 2007

Composition of Salt Water Salt water is composed of minerals dissolved during run-offs occurring over millions of years Volcanic eruptions also release minerals from inside Earth Sodium ions (Na+) and chloride ions (Cl-) are most common solids in ocean water Na+ ions and Cl- ions > 75% of all solids in ocean water Mixed and joined in the ocean, NaCl is chemical name for salt See page 370 (c) McGraw Hill Ryerson 2007

Salt water has slightly different properties than fresh water Density of Salt Water Density = how tightly packed the molecules are in an object Less dense always floats on more dense Eg. warm air rises above cool air, and oil floats on water We float better in salt water than fresh water Salt water has slightly different properties than fresh water Salt water freezes at –1.9 ºC See page 371 Take the Section 10.2 Quiz (c) McGraw Hill Ryerson 2007