Name ______Date ______

Ocean Water Composition

Saline means salty. Sea water is a saline liquid. If you accidentally gulp a mouthful of sea water, the taste may cause you to gag and cough. Let's take a closer look at the ingredients of sea water.

Don't Drink the Water

Salinity refers to the total salt content of the water. The main solid is sodium chloride, table salt. Other important dissolved solids include magnesium chloride and calcium sulfate.

Use the textbook appendix to find the Periodic Table. Using the Periodic Table, find the chemical symbols for the elements that combine to form each dissolved solid below. Place the symbols on each side of the + signs.

magnesium chloride / calcium sulfate / sodium chloride
___ + ___ / ___ + ___ / ___ + ___

How Much Salt?

Sea water contains about 3.5 percent salts. Sea water salinity varies but the composition of sea water stays the same. What may cause a change in salinity? The conditions below may increase or decrease salinity. For each listed condition, circle either INCREASES or DECREASES. Then give a reason for your choice on the line under the conditions. Use your textbook starting on page 376.

Conditions Salinity

ocean water near hot climate area / INCREASES or DECREASES
Why?
rivers flow into oceans / INCREASES or DECREASES
Why?
heavy evaporation / INCREASES or DECREASES
Why?
heavy precipitation / INCREASES or DECREASES
Why?
glaciers in sea water / INCREASES or DECREASES
Why?

Salty Puzzler:

You evaporate 2,500 grams of sea water and receive 95 grams

of dissolved salts. What was the salinity of the sea water?

Salinity: ______percent.

Is this average sea water salinity?

Circle one: YES NO.

Why or why not?

______

© 2001 by The Center for Applied Research in Education

Answer Key

SEAWATER

1. Mg + Cl, Ca + S, Na + Cl

2. a. INCREASES, Water evaporates. Solids are left behind; b. DECREASES, Fresh

water dilutes salt water; c. INCREASES, Water evaporates. Solids are left behind;

d. DECREASES, Fresh water dilutes salt water; e. DECREASES, Melting glaciers

dilute salt water.

3. Salty Puzzler: Salinity = 3.8 percent (divide 2500 by 95). This is above-average

salinity. Circle NO. A high salinity reading may indicate a hot, dry area where much

evaporation takes place.