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)
142 mL. tap water
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
149°C. 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 149°C, 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
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 100°C? To 190°C?
4. Water boils at 100°C. When it reaches that temperature, it turns to steam but the temperature does not
increase. This solution contains water, yet its temperature rose to 160°C. 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?