BACKGROUND:
The Earth's surface is 71% water and
97% of that water is sea water, while only 3% is fresh water. One
of the most significant chemical properties of water is its ability to
be a solvent. The liquid can hold in solution an exceptionally wide
range of substances, including electrolytes (salts, which dissociate into
ions in aqueous solution) and particulate matter small enough to remain
suspended in solution.
The major inorganic solutes are the positive
ions of sodium, potassium, calcium, and magnesium and the negative ions,
chloride, sulphate, and bicarbonate/carbonate. When the total concentration
of all these ions (i.e., the salinity, or salt content) is less than 3
grams per liter waters are regarded as fresh. Most fresh waters have salinities
less than 0.5 gram per liter and are dominated by calcium, magnesium, and
bicarbonate or carbonate ions. Salt waters are defined as those that
have salinities greater than 3 grams per liter.
PROCEDURE:
- Review the properties of
sea water and how it differs from fresh water. You might want to
introduce the information in the following manner:
