Experiment: Salt and Solubilities

“It is an everlasting covenant of salt before the Lord for both you and your offspring.”  Numbers 18:19

The presence of salt in the ocean has always been very interesting to ocean goers, especially since there seems to be no reason why the sea should be salty and not alkaline, or full of some other set of chemicals.  But the reality of it is that the salt in the ocean effects the physical characteristics as well as the chemical characteristics of the ocean and its life.

This experiment serves to illustrate some of the properties of salty water.  As you do the experiment, be sure to record it in your notebook.  Use the scientific method.  If you like, a report can be made using the critical thinking questions included in the procedure.

Salt and Solubilities

One of the basic reasons for a salty sea is the fact that sodium chloride is able to be dissolved in water.  But that saltiness depends upon the temperature of the water.   When water is cold less salt will dissolve in it.  When water is hot, more salt will dissolve.  The Gulf of Mexico is of higher salinity water than is the Arctic Ocean.  The Gulf of Mexico has a higher temperature than does arctic water.

You can test the solubility of salt in water in your kitchen.

Materials:

  • Salt
  • Distilled water
  • Thermometer (for older students)
  • Canning jars
  • Heat source
  • Measuring spoons

Procedure:

  1. Make ice cubes from the distilled water.
  2. Fill three canning jars with water: one with water at room temperature, another with water which has ice in it, and the last with boiling water.  Older students should use more jars with more different temperatures of water in them.
  3. Add salt by teaspoon to each of the jars, stirring between each teaspoonful until dissolved.   Count the teaspoons.  Stop adding salt when it no longer dissolves.
  4. Which jar of water dissolved the most salt?   Explain how the increase in energy of the water molecules affected the dissolution process?
  5. Make a graph showing the relation of water temperature to the amount of salt dissolved in the water.
  6. Does the salt precipitate out when the hot water cools?
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