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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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The Scientific Method

Are you doing science activities or science experiments?  Do you know it isn’t that difficult to turn an activity into an experiment?  An activity leaves out the critical thinking process that is so well formulated in the scientific method.  Use these age-adjusted steps in the scientific method to help you with your science studies by transforming your activities into experiments!

For Your Youngest Child
These questions should be asked orally.  Introduce as much vocabulary and terminology as your child has the attention span for.

What do you think will happen?
What happened?
Draw a picture of what happened and label it (with help)

For Elementary Students
These questions should be asked orally with the answers to the questions dictated by the student and recorded by the parent onto the experiment writeup or observation sheet.  If your student can write, then he should do the writing himself.  Introduce as much vocabulary and terminology as your child has the attention span for.
 
What do we want to find out?
What do you think (or guess, or hypothesize) will happen?
What do we need in order to find out the answer?
How will we test our guess (or hypothesis)?
What happened? (Use a simple chart or graph as appropriate to record results)
Draw a picture of what happened and label it.
What do you conclude from this experiment?

For High School Students
The college preparatory high school student should be using all the steps in the scientific method and producing a typed or handwritten report for his or her science notebook.  The italicized steps below require more effort and are typically reserved for a science fair project or professionally published report.
 
Statement of the Problem
Research of the Literature on the Topic
Hypothesis
Materials List
Procedure Used
Observations
Calculations
Results
Statistical Analysis
Sources of Error
Conclusions
Possibilities for Future Research