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Matter in the Sea

Clarification Statement: Examples of evidence could include adding air to expand a basketball, compressing air in a syringe, dissolving sugar in water, and evaporating salt water.

Assessment Boundary: Assessment does not include the atomic-scale mechanism of evaporation and condensation or defining unseen particles.

What is Matter?

Matter is everything around you. More specifically, it takes up space and has mass. Matter of any type can be divided into particles that are too small to see. Even then, the matter still exists and can be detected by other means (e.g., by weighing or by its effects on other objects). The amount of matter is conserved when it changes form, even in transitions in which it seems to vanish. For example, water can change states, i.e. solid, liquid, or gas, but the amount of matter stays the same (Fig. 1).

<p>Fig. 1. The same amount of water can exist in different states of matter; solid, liguid and gas.</p><br />


Matter can be understood in terms of the types of atoms present and the interactions both between and within them. The states of matter can be described and predicted based on the types, interactions, and motions of the atoms within it (Fig. 2).

<p>Fig. 2. Matter in all states is made up of particles too small to be seen.</p><br />


Matter of the Sea

<p>Fig. 3. The view of Hawaii from space shows the abundance of water on Earth.</p>The ocean covers 70% of Earth's surface (Fig.3). Seawater is a dynamic chemical mixture that has constant input of matter from the land, atmosphere, and living things. Sometimes we can see some of the materials in the ocean (Fig. 4). For example, when rainwater flows over the land, it dissolves substances from soil and rocks. Runoff carries these materials directly into the ocean or into 

<p>Fig. 4. An aerial image of the Gulf of Mexico shows runoff and resuspended sediments in the hours after Tropical Storm Ida in 2009.</p>

streams and rivers that empty into the ocean. However, particles in the ocean are often invisible to the naked eye. Rain falling into the ocean carries gases and small particles of soot and dust. Atmospheric gases mix and dissolve into seawater, especially when winds and waves churn the ocean surface. Seawater also dissolves materials from the ocean bottom, as well as materials released by underwater volcanoes and hydrothermal vents. The constant addition of dissolved substances into the ocean over billions of years has made the ocean salty.


Salt of the Sea

About 97% of all the water on Earth is salty, or saline. In fact, many lakes are even salty. You can't determine whether a body of water is salty just by looking at it because those salts are dissolved. Water is a very good solvent. Most of the water on earth, including the water in oceans, lakes, rivers, and ponds, contains many different solutes. A solution is a mixture of a solvent and solutes. In the solution of seawater, water is the solvent, salt is the solute, and the resulting saltwater is the solution (Fig. 5). Salt is a common substance that comes in many forms, including table salt, rock salt, and sea salt. When seawater evaporates, sea salt is left behind. If seawater evaporates from a surface with a slight curve, such as a watch glass or a shallow tidepool, the salt forms distinct rings (Fig. 6). The rings are made up of different types of salts in the mixture of seawater. 

<p><strong>Fig. 5.</strong>&nbsp;A close-up of salt rings on watch glass.</p><br />

Salt Harvesting

Traditionally, salt was harvested from either solar evaporation ponds or rock deposits. Salt evaporation ponds are shallow, artificial basins designed to extract salt from seawater, salty lakes, or mineral-rich springs through natural evaporation. As the water dries up, the salt crystals are harvested by raking. Salt evaporation ponds are almost entirely located in warm climates with high evaporation and low precipitation (little rain). Today, seawater is sometimes filtered to remove impurities before solar evaporation. To learn more about salt harvesting in Hawai'i, click on the Traditional Ways of Knowing special feature below.


The Salt of the Sea Vocabulary

  • Dissolve: to mix with a liquid and become part of the liquid
  • Matter: physical substance in general that occupies space and possesses mass, (especially as distinct from energy).
  • Runoff: the draining away of water (or substances carried in it) from the surface of an area of land, a building or structure, etc.
  • Saline: a solution containing salt.
  • Solute: substances that are dissolved in a solvent, like elements and compounds
  • Solvent: liquids that dissolve other substances.
  • Solution: a mixture of a solvent and solutes.




NERRS: The Salt of the Sea


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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.