Grade Level/Subject
High School Earth Space
Unit
Atmospheric & Oceanic Events
Enduring
Understanding
Atmospheric and oceanic events occur as a result
of the Earth’s motion and position with respect to
the sun.
ES 1c – Graph construction and interpretation
ES 2 – Scientific reasoning and logic
ES 10a – Water variations
SOL Objectives
Title
Oceanic Water Masses
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Lesson Objective
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Inquiry Level
Materials Required
To observe how densities of water masses
influence how they flow
To identify sources of water masses based
on their temperature and salinity
2
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4 Beakers
Plastic container/tub
Water
Food coloring
Hot plate
Ice
Salt
5 thermometers
Cardboard
Tape
Tongs to handle hot beakers or heat
protected gloves
Stopwatch
Oceanic Water Masses Lab
Objective:
 To observe how densities of water masses influence how they flow
 To identify sources of water masses based on their temperature and salinity
Background:
The world’s oceans contain layers of water called water masses. Each water mass has a source at the
surface where the water takes on specific properties, such as temperature and salinity. The water
then sinks to a certain level based on its density. Denser water will sink below water that is less
dense. In this activity you create an experiment that will demonstrate the interaction of different
sources of water in a simulated ocean basin.
Materials:
 4 Beakers
 Plastic container/tub
 Water
 Food coloring
 Hot plate
 Ice
 Salt
 5 thermometers
 Cardboard
 Tape
 Tongs to handle hot beakers or heat protected gloves
 Stopwatch
Pre-lab questions:
1. Describe density. How is it calculated?
2. Which do you believe to be denser, hot water or cold water? Why?
3. Which do you believe is denser, water with high salinity or low salinity? Why?
Directions:
1. Fill the plastic container with room temperature water to approximately 2 centimeters
from the top.
2. Take the piece of cardboard and tape the 5 thermometers so that they are approximately 23 centimeters from each other and are decreasing in height by approximately 2-3
centimeters. Be sure you can read the thermometers as you tape them.
3. Attach the piece of cardboard with thermometers halfway across the length of the plastic
bin. The bottoms of the thermometers will be submerged in the water while the cardboard
will be on above.
4. In two beakers, add hot water. In one beaker, add salt and yellow food dye. Stir to mix.
This will be the “warm, salt water”. In the second beaker of hot water, add red dye and
stir. This will be the “warm, fresh water”.
5. In the two remaining beakers, fill them with water and ice, bringing the temperature down
noticeably below the temperature of the water in the container. In one beaker, add salt and
blue food dye. Stir to mix. This will be the “cool, salt water” In the second beaker of cold
water, add green dye and stir. This will be the “cool, fresh water”.
6. Observe the temperature of the water in the container from each thermometer and record
it in your data table.
7. With your partner, carefully pour the four solutions, one beaker per corner, into the
container.
8. After the beakers have been emptied, record the temperature from each thermometer
every minute for ten minutes.
9. At the end of the observation period, create a line graph showing how the temperature
changed as the water masses flowed in the container. Your graph will have five separate
lines representing each thermometer.
Data Table:
Thermometers
Min.
0
Min.
1
Min.
2
Min.
3
Min.
4
Min.
5
Min.
6
Min.
7
Min.
8
Min.
9
1
2
3
4
5
Post-lab Questions:
1. Using your observations from the experiment, rank the four sources of water in order
from least dense to most dense.
Min.
10
2. If you had not added food dye, how would you be able to distinguish the water masses after
they entered in the container?
3. Explain why the layer of water that formed second from the top is less dense than the
water that was in the third layer from the top. How could you switch these layers in a
future experiment?
4. What could be the procedure for measuring the densities of the water masses?
5. Ocean water contains water that originated in a variety of places where the water can be
cold, warm, salty, or fresh. For each of the four water masses, give an example of a water
source that contains the properties you modeled in the experiment. (For example, the
yellow-dyed warm and salty water could represent water from a subtropical sea such as the
Mediterranean Sea.)