Solubility

Loretta Davis                  St. Agnes Consolidated School
                               1501 Chicago Road
                               Chicago Heights IL 60411
                               708-756-2333

Objective:

Fifth grade students should know how:
   1) To tell the difference between a soluble and an insoluble solution.
   2) To determine how to increase solubility.
   3) To make a saturated solution using solvents at different temperatures.

Materials:

For Demonstration:
   Supersaturated solution of sodium acetate, heat packs of sodium acetate 
solution and beryllium, cooking oil, water, sugar cubes, loose sugar, a beam
balance scale, and a hot plate.

For Students:
   Plastic cups, styrofoam cups, sugar, salt, room temperature, cold and hot 
water, breath mints, alcohol, nail polish remover, mineral oil, eye droppers, 
pieces of cotton cloth, ballpoint pens, and a stop watch.   

Strategies:   

   1) Phenomenon I - Pour a solution of sodium acetate into a clear beaker.  
Discuss what is happening and why.

   2) Phenomenon II - Each group of students examine heat packs of sodium 
acetate with beryllium.  Students are told to press hard on the beryllium.  A 
discussion is encouraged about what happens and why.

   3) The terminology: super-saturated solution, saturated solution, solute, 
solvent and solubility are introduced.

   4) Each group is given 3 styrofoam cups, 1 teaspoon and a cup of sugar, room 
temperature, cold, and hot water.  They are asked to make saturated solutions 
using each type of water and record amounts of sugar and results in a chart.

   5) Each group reports aloud.  A discussion about what increases solubility 
ensues.

   6) A demonstration of oil and water being mixed is shown.  The term 
insoluble is introduced.  A discussion about other items that are insoluble
in water is encouraged.

   7) All terminology is reviewed.  What causes an increase in saturation level 
is asked.  Different kinds of solutions are discussed. 

   8) Demonstration of surface area being a cause of the rate of increased 
solubility is shown.  Loose sugar and a sugar cube are weighed on a beam balance 
separately and then each is dissolved in equal amounts of water.  Then there is 
a discussion about surface area. 

   9) Each student is given one whole mint and two halves of a mint.  They are 
told to place the whole mint in their mouth and time how long it takes to 
dissolve.  The same is done for the two halves.  All of the students' times are 
recorded on the board.  An average for each is calculated.  The result that 
surface area makes a difference in the rate of solubility is recorded. 

  10) The three ways of increasing solubility and as a result, increasing 
saturation, are discussed.  Solvent and solute are reviewed.  The students go 
over how to remove a stain from clothing using various solvents. 

  11) Each group of students, at least 4 in a group, are given 4 pieces of 
cotton material, one ballpoint pen, 4 eyedroppers, 4 cups, one with alcohol, one 
with nail polish remover, one with mineral oil, and one with room temperature 
water.  They are asked to draw a line with the ballpoint pen horizontally across 
each swatch of material.  Then, using the eyedropper, drop 10 drops of each 
solvent separately on each piece of material, being sure to drop each drop in 
the same place.  When they are done, they are to make a chart giving each
solvent a number, one being the best at dissolving the ink, and four being the 
worst.  Each group reports their findings.  They also discuss what makes a good 
solvent.       
 
Performance Assessment:

Each student would be given the following instructions:
   You are a scientist from South America applying for a Government job here in 
the United States.  In order to get this job, you have to prove your 
qualifications.  The government administrator requires that you do the following 
test:
   You have been given a white substance imported from Africa.  You are to 
determine how to use this substance to make a saturated solution, using cold, 
hot, and room temperature water.  All of your equipment will be given to you.  
Your results must be recorded in graphic form, labeled or color-coded. 
   To prove you have administrative ability, you must also tell the three ways 
that saturation can be increased.  Naming one thing that is insoluble in water 
is also important.  Please note:  neatness and clarity and especially accuracy 
are a must.