Rate of Solubility

Sharon Barfield                Perkins Bass
                               1140 W. 66th St.
                               Chicago IL 60621
                               (312)535-3275

Objective:  
    
    This can be adapted for any grade.  Discover factors affecting the rate of 
solution. 
 
Materials Needed:  
    
    The materials are for each group of four.
1.  Test tube with cork                         9.  Sugar cubes
2.  Two clear plastic cups                     10.  Aspirin
3.  Pestle                                     11.  Salt tablets
4.  Mortar                                     12.  Mint candy
5.  Clock with second hand or stopwatches      13.  Water
6.  Alcohol burner                             14.  Alka Seltzer
7.  Goggles                                    15.  Junior Mints 
8.  Mints                                      16.  Tongs
    
Strategy:  

 1.  Introduce and discuss solvent, soluble, solute, insoluble, and rate.
 2.  Demonstrate what the students will be expected to do using the vocabulary 
     introduced.
 3.  Discuss safety and have groups get materials, including instruction sheet.
 4.  Fill containers with water as marked.  Test tubes-room temperature;
     Cups-one room temperature, one cold.
 5.  One solute will be dropped into each solvent.  Make a hypothesis about 
     what will happen before adding the solutes.  
 6.  Place one test tube over the flame, holding it with the tongs.  Place the 
     cork in the second tube and shake. 
 7.  Use the mortar to crush the solute and put it in the cup containing room 
     temperature water.  Drop a solute into the cold solvent and let it sit. 
 8.  Record the length of time needed to dissolve the solvents.  If a solvent 
     hasn't completely dissolved in 5 minutes write 5+ on your chart and discard 
     all solvents.
 9.  Repeat steps 4 through 7 for the remaining solutes, except for the Junior
     Mints.
10.  Pass out a new set of instructions and the Junior Mints.
11.  Each student will place one Junior Mint in his/her mouth.
12.  Do not move it around.  Time how long it takes for it to dissolve.  Write
     down every member's time.  
13.  Now put one in your mouth and move it around.  How long did it take to 
     dissolve?  Write down the fastest time for the group.
14.  The group members with the fastest time will compete against each other.
15.  Put a Junior Mint in the mouth and move it around.  The one who dissolves
     the mint first is the winner.
16.  Discuss what took place.  Discuss whether their hypotheses were correct.
17.  Review vocabulary and factors that affect the rate of solubility.     
18.  Have the students act out what the molecules of the solute are doing when 
     a solvent is being heated, when it is cold, when it is being shaken, and 
     when it is just sitting at room temperature.  

Performance Assessment:

Given an unknown solute, determine which method used in the experiments will
be fastest in dissolving the solute.  The group dissolving it first will receive 
extra credit points.
                                      
Conclusion: 

The students will discover which method works the fastest to dissolve a solute 
and be able to apply the information gathered to real life situations.