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Earth Science
N47
Ocean Water and Salinity
Instructions: Read the below passage completely. Then, answer the questions below
the passage IN COMPLETE SENTENCES!
Composition of the World’s Oceans
Ocean water contains more than just water. The main substance dissolved in ocean water is
sodium chloride (NaCl). Sodium chloride is ordinary table salt. Dissolve means that a
substance is mixed into another substance. The substance that is dissolved must look like it
has completely disappeared in the other substance.
Concentration is the amount of one substance in a certain amount of another substance.
The concentration of table salt in ocean water is about 2.7%. This means that 100 grams of
ocean water holds 2.7 grams of sodium chloride (table salt).
Ocean water also contains other salts besides regular table salt. We can use the term
salinity to describe the concentration of ALL salts in ocean water. Salinity means the total
amount of dissolved salts in a water sample. The salinity of ocean water is about 3.5%. This
means that 100 grams of ocean water can have about 3.5 grams of salt dissolved into it.
The solid substances dissolved in sea water come from various sources. Some substances
are washed into the water from rivers and streams. Some substances are deposited in the
water as waves pound rocks on the shore. Other substances come from erupting volcanoes
and steaming hot springs that dot the ocean floor.
1. What is the definition of concentration?
2. What does the term salinity mean?
3. What is the salinity of ocean water? What does this mean?
4. Where do the solid substances (such as salt) in sea water come from? Be specific!
5. If a substance dissolves into another substance, would you be able to tell just by
looking at the substance?
6. Is the salt that you eat at a dinner table the same salt that is dissolved in the sea?
7. If you have 100 grams of ocean water, how much total salt is probably dissolved
in it?
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