Name_______________________________________________________ Block_______ Date_____________
Salinity Lab
MATERIALS:
 Large, Med. & Small sized beakers
 Salt
 water
 Green, blue & red food coloring



two spoons
two droppers
colored pencils for sketches/graph
DIRECTIONS:
Part I
1. Fill large beaker ½ full with clear tap water.
2. Fill small beaker ½ full with water. Add 1 level spoonful of salt. Add one drop of green food
coloring. Mix well.
3. Fill dropper with green water. Slowly place several drops of salty green water into the
beaker with clear water.
4. Observe the motion of the green water. Sketch & Record observations:
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5. Empty/rinse both beakers.
Part II
6. Fill large beaker ½ full with clear tap water. Add 2 level spoonfuls of salt. Mix well then let
water set still.
7. Fill medium beaker ½ full with water. Add one drop of blue food coloring. No salt. Fill
dropper with blue water.
8. Slowly place several drops of blue tap water into the beaker with clear salt water.
9. Observe the motion of the blue water. Sketch & Record observations:
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**DO NOT EMPTY BEAKERS!**
Part III
10. Slowly place several more drops of blue tap water into the beaker with clear salt water until a layer of blue
water forms on top.
11. Fill the small beaker ½ full with water. Add two drops of red food coloring. Add 2 level
spoonfuls of salt. Mix well. Making sure that the dropper is clean, fill the dropper with red water.
12. Carefully place the dropper into the layer of clear water (try not to disturb the blue layer)
and slowly squeeze out several drops of salty red water.
13. Try dropping some red drops above the surface through the blue water layer.
14. Observe the motion of the red water. Sketch & Record observations:
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15. Finally, mix the layered water system together.
16. Record observations: ___________________________________________________________________
Name_______________________________________________________ Block_______ Date_____________
CONCLUSION:
Temperature and salinity (the amount of dissolved salts in the water) affect the density of the water. Ocean salinity differs
by small numbers, so oceanographers need to be accurate when measuring salinity. In oceanography, salinity is
measured in mg/L or ppm (parts per million). Changes in density caused by wind and currents at the surface affects the
deep-ocean currents. Density ultimately affects the objects that exist in the water, such as whales, seaweed, and
submarines. The saltier the water, the more buoyant an object becomes. Therefore, salt waters are constantly trying to
find their "place" in the ocean according to their salinity. Very salty water is more dense, and will sink more, thus very salty
water is found at the bottom. Less salty water is less dense and will float on top of the more dense salty water. Of course
the layers are more complicated than this, but in this activity, you should have seen that salt or fresh water drops are
going to want to "hang out" in water with similar properties. So fresh water drops will rise to the fresh water layer and salt
water drops will sink to the salt water layer. The salinity of the water mixes, or changes, only when vigorously stirred. The
U.S. Navy pays close attention to ocean salinity to be sure they know how submarines will travel as they move through
the different waters of the world.
SUMMARY QUESTIONS:
1. In Part I, what happened to the drop of salty green water in the tap water? Why?
2. In Part II, what happened to the drop of blue tap water in the clear salty water? Why?
3. Why did the blue tap and clear salty water not mix together?
4. In Part III, what happened when the very salty red water was added to the layers? Why?
5. What units do oceanographers use to measure salinity?
6. Why is this information important?
7. Who would this information be important to?
8. Table 1 lists the approximate surface water salinities at various latitudes in the Atlantic and
Pacific Oceans. Using the data construct a salinity curve for each ocean. Use different colored
pencils for each ocean!
Salinity (ppm)
The Relationship between Latitude and Salinity
33
3
32
31
Color Key
Atlantic Ocean:
20oN
10oN
0
10oS
20oS
Latitude
Pacific Ocean:
9. At which latitudes are the highest surface salinities found? Suggest a reason why.
10. Of the 2 oceans, which has the higher average surface salinity?
Suggest a reason for the difference in average surface salinities between the oceans.