Reflection: Grappling with Complexity Starch in Liquids - Section 2: Independent Practice

 

When I ask students to complete this laboratory work, I deliberately do not tell my students how to idenitfy a positive test result. Not knowing exactly what to look for during the test process encourages students to actively observe during the test process and also encourages student discourse about observable changes.

In this lab, when iodine is added to a starch containing liquid, the liquid turns black (positive result). Liquids that do not contain starch (negative test result) show little to no color change. There are liquids (corn oil) which partially change color but do not appear black. Students struggle with what to do with tests that are in between the positive and negative results they expect. I spend time at the end of the lab sharing and dicussing test results to help students grapple with this unexpected complexity. I allow students to label the corn oil test as either positive or negative as long as they use observational data to justify their thinking.

 

  Identifying Positive and Negative Test Results
  Grappling with Complexity: Identifying Positive and Negative Test Results
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Starch in Liquids

Unit 7: Food Chemistry
Lesson 2 of 11

Objective: SWBAT identify liquids that contain starch using a scientific investigation.

Big Idea: Starch containing foods provide energy for the human body.

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