Christmas Lab: Chemistry Lab: Crystallization of a Supersaturated Sucrose Solution

Abstract:  Tell WHAT you are going to do and HOW you are going to do it.  Be sure you include the scientific terms for what you are going to be discovering.  Read the entire lab before you write. (HINT: observe the behavior of a sucrose solution at 150 C and at  23 C but that's not ALL you need!)  Remember, information and explanations go in the Introduction.  This is brief.
 
Introduction:  Define the following terms in your introduction: sucrose, solution, saturated, supersaturated, crystallization.  Remember, the reader has NO IDEA what any of these concepts are, or what you are going to investigate.  A good test of your abstract and introduction would be to let a non-chemist read them and see if they can explain the experiment to you when they finish reading.  The introduction will probably be several paragraphs.

Materials: items with ** will be brought from home by each lab group. (you may store them in the back room)
 

*Equipment 

Goggles, apron 
*1  1-lb. coffee can 
*1  stirring utensil (old spoon with long handle) 
Meter stick 
Bunsen burner or hot plate 
Ring stand and ring clamp 
Wire gauze *(reduces scorching) 
Thermometer 
Waxed paper  (approx. 100 cm.) 
Beaker tongs 
Baggie (if you want to take the product home)

Chemicals 

142 mL. tap water 
*248 mL. sucrose 
*110 mL. liquid dextrose 
*approx. 15 mL. margarine 
2 drops food coloring 
*3 mL extract OR 6-10  mL. flavoring

PRELAB:  Prepare a chemical data table for water, sucrose, and dextrose. Read the questions and prepare a table for all of your observations.  Be sure it is easy to read.

Procedure:     ***DO NOT MESS AROUND! COOKING TIME CAN BE LENGTHY!!
1. Put on goggles and aprons.
2. Measure sucrose into coffee can.
3. Measure liquid dextrose and add to sucrose.
4. Measure water in beaker. Swirl gently to remove all traces of dextrose from the beaker, then add to
     dextrose and sucrose.
5.  Measure 8 mL of margarine and add to mixture.  Stir.  Does the sucrose dissolve completely? Does the
     lubricant mix with the water? RECORD YOUR OBSERVATIONS.
6. Heat mixture CAREFULLY over Bunsen burner until it boils,  stirring constantly, until it reaches
    149C. CAUTION: THIS IS VERY HOT!  Meanwhile, spread a very thin film of margarine on a 100 cm. length
    of waxed paper.
7. When mixture reaches 149C, remove from heat and allow to cool to about 125 C. Add food coloring and
    flavoring, stirring until well mixed. Pour onto waxed paper. Spread the mixture in a layer 1-1.25 mm.
    thick.  Record observations of physical state before and after cooling.
8. CLEAN UP while waiting for product to cool.  *No credit will be given for lab until your work area has
    been inspected.

QUESTIONS: Answer in complete sentences that include the question.
1. Describe what you saw as the solution heated.
2. At about what temperature was all of the solute dissolved?
3. What do you think would happen if you heated the mixture only to 100C?     To 190C?
4. Water boils at 100C. When it reaches that temperature, it turns to steam but the temperature does not
    increase.  This solution contains water, yet its temperature rose to 160C. How could you explain this?
5.  At what point in the procedure was the solution supersaturated?
6. Why was it necessary to cool the solution before adding the extract or flavoring oil?  (hint: think about
    the nature of the ingredients in the flavoring.)
7.  What evidence do you have that the solution was supersaturated?  That it crystallized?