Hot, Cold, Fresh and Salty

Notes from our reviewers

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• 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.