Education: The Role of Salt

STUDENT OUTCOMES
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Compare the basic properties of fresh and salt water (e.g., density, ability to dissolve salt, freezing point) (NSES,134,160; OLS,10)
Explain that evaporation can separate the water from the salt in salt water (NSES,127; NAAEE,16; OLS,13)
Concept map
Concept Map: Phases of Water Understand various forms that water can take
Concept map
Concept Map: Heat Capacity Learn how heat affects water
Concept map
Concept Map: Hydrologic Cycle Make connections with the water cycle
What Role Does Salt Play in the Basic Properties of Water?
A defining characteristic of ocean water is its relatively high concentration of dissolved salts or salinity. These concept maps, activities and videos focus on relationships between salt and water, including water properties, phases, heat capacity and the hydrologic cycle. These resources will help to organize information into meaningful patterns that students can use for future problem solving. The interlinked concept maps are provided to illustrate that salinity-related processes do not exist in isolation: each depends on its relationships to others for broader meaning (i.e., square concepts provide direct links to other maps in the series).

Featured Concept Map: Properties of Water

Hands-On Activities
Movies
Podcasts
FAQs
  • In the global water cycle, is "salty" good?

    • There's no such thing as absolute good or bad, right? In certain areas, you want to monitor the change, that's really the key. You want to see whether the area's freshwater gets fresher, you know, and if the salty water gets saltier. That represents the speeding up or slowing down of the water cycle. So you ask the questions: do we have more evaporation as we change the climate? Do we have more freshwater melting? All these questions are related.
      Yi Chao, Aquarius Project Scientist, NASA Jet Propulsion Laboratory in Ocean Bights Interview with Yi Chao, The Magazine of the Catalina Marine Society (CMS), Vol. 2, No. 2 (Interviewer: Chris Howell).
  • I understand that (Aquarius) is able to collect data that, for over a hundred years, has been collected by buoys, ships, etc. I'm assuming this instrument will collect data in a more accurate and thorough way and in areas that (we) haven't been able to do before. Are the data going to be useful in comparing what the salinity levels have been in the past? Or is it from just this point on that we'll be able to measure salinity since the older methods might not be as accurate?

    • That's an extremely insightful and thoughtful question. Since the dawn of civilization, salinity measurements have been made rather sporadically: at points and intermittently in time, and with varying accuracies. What Aquarius/SAC-D will be doing is making global measurements frequently and with high precision, high accuracy and high stability. There are places in the ocean - particularly in the northern hemisphere - where we have almost enough salinity measurements in the past to be able to continue a "time series" as (the person who asked the question) pointed out with Aquarius/SAC-D. However, over vast reaches of the earth's ocean - especially in the southern hemisphere and the southern oceans - these will be the first measurements. So it's a combination of extending our knowledge and improving those measurements in some areas where we already have "barely reasonable" measurements (and) extending excellent measurements to areas where we have never measured before.
      Michael Freilich, NASA Earth Science Division Director.
  • Why does freshwater give off more energy than saltwater?

    • It's a little bit complicated in engineering terms but I'll see if I can make this clear: conductivity is what makes currents flow. So something that has good conductivity, like the wires in your house, conduct electricity very well. If something has poor conductivity, like a glass window, it doesn't conduct electricity well at all. It turns out that the saltiness of seawater increases its conductivity. That conductivity suppresses the energy that's emitted from the ocean surface. Actually, what happens is that (the energy) bounces off the surface and back into the ocean; so the more conductivity, the more energy is retained (i.e., bounced back into the ocean).
      David Le Vine, Deputy Principal Investigator in How Do We Cover the Globe with Aquarius Data? NASA's Aquarius Studies Our Salty Seas Webinar, January 17, 2012 (Session 2).
  • Why do you think that the Atlantic Ocean has a higher salinity content than the Pacific Ocean?

    • The Atlantic experiences a higher amount of evaporation; the same is true for the Mediterranean Sea, where salinity is as high as 37-39 PSU.
      Yi Chao, Aquarius Project Scientist, NASA Jet Propulsion Laboratory in Inspire Chat with Yi Chao (Host: Jim Gerard).