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Title
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Layering with Salt
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Type
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Primary: Laboratory
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Operation
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Resilient Planet
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Mission:
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Mission 3: Paradise Lost
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Print Page
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57
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Subjects
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Science | Physical science | Properties of materials | Chemical properties | Physical properties | Science as inquiry | Science process skills | Modeling | Predicting
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Grades
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5 | 6 | 7 | 8
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Keywords
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layer, salt, Chesapeake Bay, Sylvia Earle, biotic, abiotic, characteristic, salinity, watershed, structure, halocline, density, fresh, water, observe, wave, stable, thermocline
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Duration
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00:30:00 (HH:MM:SS)
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Audience
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Teachers | Elementary Grades | Junior High
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Created On
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4/20/2008
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Copyright
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NASA
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From: Resilient Planet Mission 3: Paradise Lost (pp: 57) |
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Layering with Salt In this activity, the students get to construct a halocline to observe the formation, structure, and behavior of this layer. |
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To understand the ecology of the Chesapeake Bay, Sylvia Earle must consider its biotic and abiotic characteristics. An important part of the Bay's abiotic structure is the water's salinity profile. Water that flows into the Bay from the surrounding watershed has little measurable salinity. In contrast, water that enters the Bay from the Atlantic has the salinity of ocean water. When volumes of fresh and salt water meet within the Bay, they do not freely mix. Instead, they remain somewhat separated and form a relatively stable structure. At their boundary is a layer in which salinity rapidly changes. An area where salinity rapidly changes is called a halocline. In this activity, you will use a clear plastic drawer to observe the formation, structure, and behavior of this layer.
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| Materials |
- Lab 2 Data Sheet
- blue food coloring
- two 250-mL beakers
- plastic drawer with divider insert (from workspace organizer)
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| Lab Prep |
- Describe the concept of density. How do dissolved materials affect the density of a fluid?
- Compare and contrast the density of fresh water with that of salt water.
- How might a density difference between two volumes of water affect their mixing? Explain. What factors might affect the stability of water layers?
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| Make Observations |
- Fill two 250-mL beakers with about 200-mL of water. Saturate the water in one beaker with table salt. To do this, add several tablespoons of salt. Stir until the salt is dissolved. Continue adding and stirring salt until it no longer dissolves in the water but collects on the beaker bottom.
- To the other beaker, add several drops of blue food coloring to produce a deep, dense color.
- Insert the plastic divider into the plastic drawer so that it separates the compartment into two side-by-side chambers.
- Carefully fill one chamber with the clear, salt water. Fill the other chamber with the dyed fresh water.
- Make a prediction. What will happen when the divider is removed?
- While observing the drawer from the side, quickly remove the divider. What happens?
- Did you observe any internal waves produced during the formation of the halocline? If so, describe what you saw and how it affected the formation of the halocline.
- Make a prediction about how long the observed structure will remain stable. Test your prediction.
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| Extension |
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A thermocline is a distinct layer that is part of water's vertical structure. In a thermocline, the temperature changes rapidly and isolates upper and lower regions of differing temperatures. Based on what you observed in this lab, create a lab that can be used to model the formation and behavior of a thermocline.
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Journal Question
Describe several different ways a halocline might affect the living components of the Bay's environment. | |
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