Page 25 - Curriculum Visions Dynamic Book

Technology
Beaker of water with phenolphthalein indicator added
Sodium pellet
Geology
Sodium makes up about 3% of the Earth’s crust. Sodium is also found in all stars.
Sodium does not occur as a native metal because it is too reactive. Its compounds are naturally dissolved in
sea water and lakes with inland drainage. Inland lakes and coastal lagoons develop very high concentrations of sodium salts as water evaporates. In time, these salt accumulations form evaporite deposits. The most common mineral in this group is rock salt, sodium chloride, known as the mineral halite.The nitrate is known as Chile saltpetre.
Biology
Sodium is an essential element for life. As an ion, it is important in helping substances move across cell walls and so leave the bloodstream. It is also essential for nerve activity.
In animals, sweating results in loss of sodium (as does excessive loss of body fluids during dysentery). Natural diets contain enough sodium for health, but processed foods are
high in sodium. As a result, many people consume two to three times their need for sodium.This can result in high blood pressure.
 Sea salt, obtained
from evaporation, can be produced in large crystals. They are then ground down for use at the table.
Sodium metal is hard to use directly because it reacts so readily in air. Sodium was part of the lead compound that was an antiknock ingredient in petrol in the days before unleaded petrol. Its use has now been discontinued in industrial countries. It is also used in the extraction of titanium from its chloride ore (sodium and chloride combining to make common salt, while the titanium is left
as a free metal).
Sodium also goes into the preparation of organic compounds. Sodium vapour is in the street lamps that give out a characteristic orange glow.
Sodium chloride (common salt) adds flavour to foods and preserves them (it works by absorbing the water in microbes and dehydrating them). Soda ash is sodium carbonate; baking soda is sodium bicarbonate (baking powder); caustic
soda is sodium hydroxide, used as a way of removing grease. Sodium salts are used in soap making.
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