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Hot, Cold, Fresh and Salty

Jerry Roth, NOAA Ocean Service

The NOAA Ocean Service Education lab requires students create and manipulate solutions simulating different ocean water characteristics in order to recognize that the effects of salinity and temperature are the drivers of thermohaline circulation.

Activity takes two to three 40-minute class periods. Additional materials required.

Learn more about Teaching Climate Literacy and Energy Awareness»

ngssSee how this Activity supports the Next Generation Science Standards»
Middle School: 1 Performance Expectation, 2 Disciplinary Core Ideas, 7 Cross Cutting Concepts, 5 Science and Engineering Practices

Climate Literacy
About Teaching Climate Literacy

Ocean as climate control, oceanic conveyor belt; abrupt changes in thermohaline circulation
About Teaching Principle 2
Other materials addressing 2b

Excellence in Environmental Education Guidelines

1. Questioning, Analysis and Interpretation Skills:B) Designing investigations
Other materials addressing:
B) Designing investigations.
1. Questioning, Analysis and Interpretation Skills:C) Collecting information
Other materials addressing:
C) Collecting information.
2. Knowledge of Environmental Processes and Systems:2.1 The Earth as a Physical System:A) Processes that shape the Earth
Other materials addressing:
A) Processes that shape the Earth.
2. Knowledge of Environmental Processes and Systems:2.1 The Earth as a Physical System:B) Changes in matter
Other materials addressing:
B) Changes in matter.
2. Knowledge of Environmental Processes and Systems:2.1 The Earth as a Physical System:C) Energy
Other materials addressing:
C) Energy.

Notes From Our Reviewers The CLEAN collection is hand-picked and rigorously reviewed for scientific accuracy and classroom effectiveness. Read what our review team had to say about this resource below or learn more about how CLEAN reviews teaching materials
Teaching Tips | Science | Pedagogy | Technical Details

Teaching Tips

  • Educators should make sure that the link to the thermohaline circulation (and to currents, weather and climate) is clear to the students.
  • Students may have difficulty in creating layers of water of different temperatures and salinity. They may need practice and/or guidance.
  • Make sure that students add food coloring to different temp/saline solutions so they they can see layers.
  • An extension activity can be found here: http://www.classzone.com/books/earth_science/terc/content/investigations/es2202/es2202page01.cfm.
  • To maximize use of class time, have some related seat work for students to do or lecture notes to discuss during the time it takes for the solutions to cool/warm.
  • Modify student worksheets to ask students to justify their predictions (i.e. what is your prediction and why?)

About the Science

  • A good demonstration of the chemistry and physics that make the thermohaline circulation possible in the ocean.
  • Links to supporting background information provided.
  • Comment from expert scientist: The practical nature of the experiment is a very strong visual demonstration to students about the relative importance of temperature and salinity to determine the density of ocean water. It brings together a basic understanding of how the density of water can change due to these two factors in a simple experiment that everyone can repeat and visualize.

About the Pedagogy

  • This is a lesson developed by a master teacher. The comments in the lesson will be useful to other teachers.
  • Individual learning goals are well-written and clear.
  • Section on prerequisite knowledge is clear and provides additional supporting references.
  • A link to an extension activity is provided.

Technical Details/Ease of Use

  • This is a straightforward lesson with clear points that should be apparent if done as recommended by the instructions.
  • Very clear instructions for teacher and students.
  • Student worksheet needs to be copied and pasted into a MS Word document.
  • Students will need careful guidance when mixing liquids or else desired results will not be seen.

Next Generation Science Standards See how this Activity supports:

Middle School

Performance Expectations: 1

MS-ESS2-4: Develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity.

Disciplinary Core Ideas: 2

MS-ESS2.C3:Global movements of water and its changes in form are propelled by sunlight and gravity.

MS-ESS2.C4:Variations in density due to variations in temperature and salinity drive a global pattern of interconnected ocean currents.

Cross Cutting Concepts: 7

Systems and System Models, Energy and Matter, Structure and Function, Stability and Change, Patterns, Cause and effect

MS-C1.2: Patterns in rates of change and other numerical relationships can provide information about natural and human designed systems

MS-C2.2:Cause and effect relationships may be used to predict phenomena in natural or designed systems.

MS-C4.2: Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy, matter, and information flows within systems.

MS-C5.2: Within a natural or designed system, the transfer of energy drives the motion and/or cycling of matter.

MS-C5.4:The transfer of energy can be tracked as energy flows through a designed or natural system.

MS-C6.1:Complex and microscopic structures and systems can be visualized, modeled, and used to describe how their function depends on the shapes, composition, and relationships among its parts; therefore, complex natural and designed structures/systems can be analyzed to determine how they function.

MS-C7.3:Stability might be disturbed either by sudden events or gradual changes that accumulate over time.

Science and Engineering Practices: 5

Developing and Using Models, Constructing Explanations and Designing Solutions, Obtaining, Evaluating, and Communicating Information, Asking Questions and Defining Problems

MS-P1.1:Ask questions that arise from careful observation of phenomena, models, or unexpected results, to clarify and/or seek additional information.


MS-P6.2:Construct an explanation using models or representations.

MS-P6.4:Apply scientific ideas, principles, and/or evidence to construct, revise and/or use an explanation for real- world phenomena, examples, or events.

MS-P8.5:Communicate scientific and/or technical information (e.g. about a proposed object, tool, process, system) in writing and/or through oral presentations.

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