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Salt from the Sea
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Salt from the Sea

Credit: Sandip Dey
Source: http://commons.wikimedia.org/wiki/File:Salt_pans_in_Marakkanam,_India.jpg
License: CC BY-NC 3.0

This photo shows a salt field. Something is produced in this field, but it’s not crops. It’s salt from seawater.

The Back Story

  • Did you ever wonder where the salt in your saltshaker comes from? Solid sodium chloride consists of mineral crystals. Is this mineral mined from rocks like most other minerals?
  • Actually, most of the sodium chloride we use comes from the sea. Ocean water is a homogenous mixture of salt in water. It contains about 3 percent sodium chloride.
  • Ocean water is the type of mixture called a solution, because the salt is dissolved in the water. Water is the solvent, and sodium chloride is the solute. Water dissolves salt when water molecules attract and pull apart the sodium and chloride ions in salt crystals.
  • The different substances in a mixture retain their unique properties. They can also be separated by physical processes. How do you think salt could be separated from ocean water? Watch the video “Sea Salt Distillation” at the following URL to see how it’s done: 

http://www.hendoscience.com/video-clips-separating-mixtures.html

Show What You Know

Learn more about separating salt from seawater at the link below. Be sure to watch the slide show as well as read the article. Then answer the questions that follow.

  1. What conditions are ideal for removing salt from seawater using solar energy?
  2. What process is used to separate the salt from seawater in this type of operation? What conditions in question 1 help this process occur?
  3. Why is each reservoir a mini ecosystem? Describe how the ecosystems vary.
  4. Seawater is pumped or flows from one reservoir to another as it becomes increasingly concentrated with salt. At what concentration does sodium chloride start to come out of the solution and form solid crystals of salt?
  5. How long does it take for the process to produce salt crystals from seawater?
  6. How is the salt harvested? What happens to it after that?
  7. Besides food preparation, what are some other uses of salt?

Image Attributions

  1. [1]^ Credit: Sandip Dey; Source: http://commons.wikimedia.org/wiki/File:Salt_pans_in_Marakkanam,_India.jpg; License: CC BY-NC 3.0

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