Grades: 11-12, Chemistry
Author: Jessica Cleaver
Source: This material is based upon work supported by the National Science Foundation under Grant No. EEC-1161732.
Students should investigate which starches will create the "best" pie. They will first brainstorm what qualities they would like to have in a custard-type pie, they investigate the properties of different commercially available starches like corn and potato in order to develop a recipe for making a "pie filling" sample that exhibits the desired properties. Students can then further investigate how the human body digests the different components of the starch (amylose and amylopectin)
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Pre-assess students understanding of gels by providing samples of several everyday gel products and asking the students to categorize them according to their state of matter. Provide them the opportunity to use some of the same testing methods on a known gel sample such as gelatin and describe the results. Brainstorm the desired properties of a gel for a pie filling and devise a method for preparation and testing. Teacher should provide a "recipe" for pie filling and the students should do the calculations to scale down the recipe and convert to SI units. The teacher should divide the students into groups so that each group can test different types of starch.
After the teacher approves of the plan, students will carry out an experiment to create gels of the desired consistency.
Students should explain how the different polymers in the starch (amylopectin-branched polymer and amylose-little branching/linear polymer) affect the final gelation properties of the pie filling. They should create a report showing the properties and results of their experiment including the stability of the gel and how the Tyndall effect is demonstrated. In order to test the starch in the gel, Luegel's reagent can be used along with a colorimeter (if available.) If practical, they could also make a pie using their recipe and fill out a questionnaire (student designed) that evaluates the effectiveness of the recipe.
Students should design a way to test for other desired properties such as shelf life. Students interested in health can investigate how different components of starch (amylose and amylopectin) affect the body differently and formulate a pie filling that is healthier for diabetics or people with food allergies.
A basic understanding of states of matter, dimensional analysis.
Common Core Standards:
Dietary planning and nutrition
"green" plastics industry
Varies with the class environment and level of student: could simply be completing the worksheet, completing a formal lab report according to normal class requirements, or doing the extension projects.
Grouping Suggestions: Since students will be designing a method for testing properties that are related to health or food service, dividing students into groups of similar interest or future plans makes sense. Make sure that at least one student in each group is strong in math skills.
Pacing/Suggested Time: Most of the gels take about 15 minutes to form but they will need to cool to room temperature to test the proper properties. Altogether, the lab and the research should take approximately 3 40-minute class periods. If the extension of research option is taken, 1-2 weeks additional time to do the projects would be appropriate.