Around 72% of the Earth is water. This includes both fresh water
and salt water. Only 3% of this water is fresh water, with 2.6% of
it in a solid state. Ocean salt water has an average salinity of 3-4%.
Salinity is a measure of the quantity of dissolved salt in water.
This is not a rule. The Dead Sea, for instance, is a 30% salt solution,
which is quite remarkable.
The concentration of salinity is measured in both percentages and
g/L.Fresh water must have a salinity of less than 1%.An example of
fresh water is the Great Lakes.
Salt water has a higher density than fresh water. Remembering buoyancy,
if an object is more dense than the liquid it is placed in, it will
sink, and vice versa. Thus, in the Dead Sea, as the water has such
a high salinity, the water is more dense than a human body, allowing
swimmers to float very, very easily.
Desalination is any method of removing salt from water, thus making
pure water and solid salt. So far, there are two ways in which desalination
can occur. Firstly, water can be evaporated and then condensed to
remove the salt. Although this is very simple, it requires a great
deal of thermal energy, which is expensive. As a result, some stations
use solar energy or geothermal energy. The second method is newer,
and uses osmosis. Water particles pass through a membrane with nanotubes,
which are tube-like pores. However, the salt particles and other large
particles, excluding those of water, can not pass through. This basically
filters the salt from the water. |
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