Properties of Ocean Water

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  • 0:07 Ocean Water
  • 0:33 Salinity and Chemical…
  • 2:59 Ocean Water Temperature
  • 3:53 Ocean Water Density
  • 4:28 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Ocean waters are salty and contain minerals and dissolved gases. They also have a high heat capacity and vary in density depending on temperature and salinity. Learn more about the unique chemical and physical properties of ocean water.

Ocean Water

Did you ever wonder why ocean water is so salty? Did you know that the freezing point of ocean water is not 32 degrees Fahrenheit like ordinary freshwater? Did you know that ocean water is actually layered, and that dense ocean water sinks to the bottom while lighter water floats on top? Ocean water has some unique properties, and in this lesson, you will learn about the properties of ocean water, including salinity, temperature and density.

Salinity and Chemical Properties

If you look at earth from space, you will notice that much of the planet is covered in water. The vast majority of this water, about 97%, is found in oceans, and we cannot use it for drinking, cooking, or watering our flowers. The reason this water is not useful in these ways is because it has a high salinity, which is the amount of salt dissolved in water. In other words, ocean water is salty. If you ever went swimming in the ocean and accidentally took a big gulp of ocean water, this fact was unpleasantly obvious.

But why is ocean water salty? Well, most of the salt that ends up in the oceans originated on land. Rain, as well as moving water in rivers and streams, washes over rocks containing the mineral sodium chloride, which you know as common table salt. The salt is then carried into the oceans. Salt can also find its way into oceans through underwater volcanoes that stir up salt and other minerals from deep layers of the earth.

The salt in oceans becomes more concentrated over time as water from the surface of the ocean evaporates, leaving the salt behind. Salt is the main chemical ingredient in ocean water, but it also contains other chemicals, such as magnesium, sulfate, calcium and potassium. Many scientists believe that life began in the oceans, so it's not surprising that chemicals found in seawater are important chemicals needed to sustain life.

There are also gases dissolved in ocean water, including nitrogen (N2), oxygen (O2) and carbon dioxide (CO2). Nitrogen is found in fertilizer and used to enhance the growth of plants in a farmer's field. If nitrogen-containing fertilizer runs off of farmer's fields and makes its way into ocean waters, it can cause some ocean plants to grow like crazy. These plants end up using more than their fair share of dissolved oxygen, which can suffocate other ocean creatures such as crabs and fish. This illustrates one way human activities impact the oceans.

Oceans act as carbon sinks, which means that they are natural environments that absorb and store carbon dioxide. So oceans remove carbon dioxide, which is a greenhouse gas, from the atmosphere, making them important players in the study of global climate changes.

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