(CHO) Salinity Now! Lesson

Salinity Now! 

Simply said, ocean water is salty. Ocean water contains salts carried from rivers or from erupting volcanoes that make the water salty. The "saltiness" of the ocean is termed salinity. Salinity is the total salt content measured in parts per thousand (ppt). The average salinity of the Earth's ocean is 35ppt, which means that there are 35 pounds of salts per 1000 pounds of water. Ocean water contains magnesium, sulfate, potassium, calcium, and other minor elements. But the most abundant salt ions are sodium and chloride, which make up 85% of the dissolved salts in ocean water.

Sea water is about 96.5% pure water and 3.5% dissolved solids and gases. These dissolved solids change the chemical properties of the water, thus changing some of the water's characteristics. One such example is that it takes less energy to evaporate sea water than pure water. The dissolved solids also inhibit the formation of the crystal structure during freezing. The saltier the water, the lower the freezing point. Therefore, as seawater freezes, the ice formed is almost pure water.

Most organisms can not use sea water as drinking water. Marine organisms have special adaptations to utilize the water found in the oceans. But terrestrial and freshwater organisms can not use salt water for consumption. Consuming salt water will actually make the organism dehydrated. 

To help solve the problem of water shortages, scientists have begun to examine different ways of taking the salt out of salt water. Desalination is the process of removing salt from ocean. One way to remove the salt from ocean water is to evaporate the seawater and collect the freshwater that condenses from the resulting steam. When the water evaporates, the salt will be left behind separate from the pure water collected.

Another way to desalinate water is to use glaciers. When sea water freezes, the ice formed is nearly fresh water. The salt once in the water remains under the ice, making the remaining water very dense and salty, but the ice is nearly pure.

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