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Hot, Cold, Fresh and Salty
http://oceanservice.noaa.gov/education/lessons/hot_cold_lesson.html

Jerry Roth, NOAA Ocean Service

In this activity, learners observe the effects of the layering of warm and cold water and water that is more or less saline than regular water. They will discover how the effects of salinity and temperature are the root cause of thermohaline layering in the ocean.

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

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Climate Literacy
About Teaching Climate Literacy

Covering 70% of Earth's surface, the ocean exerts a major control on climate by dominating Earth's energy and water cycles. It has the capacity to absorb large amounts of solar energy. Heat and water vapor are redistributed globally through density-driven ocean currents and atmospheric circulation. Changes in ocean circulation caused by tectonic movements or large influxes of fresh water from melting polar ice can lead to significant and even abrupt changes in climate, both locally and on global scales.
About Teaching Principle 2
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Excellence in Environmental Education Guidelines

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

Benchmarks for Science Literacy
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Climatic conditions result from latitude, altitude, and from the position of mountain ranges, oceans, and lakes. Dynamic processes such as cloud formation, ocean currents, and atmospheric circulation patterns influence climates as well.
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In a fluid, regions that have different temperatures have different densities. The action of a gravitational force on regions of different densities causes them to rise or fall, creating currents that contribute to the transfer of energy.
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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.

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