Lesson #6: Limiting Reactants and Percent Yield

Lesson Details Subject: Science Learning Level: High School Author(s): Geri Anderson-Saxton, Melissa Chardeen Submitted by:

Abstract This lesson will introduce students to the concept of limiting and excess reactants (too little of one reactant; too much of another). Additionally the students will be introduced to % yield: the concept that the actual amount of product made may be different from the theoretical calculations. These are covered in class and then the students use this knowledge to modify their recipes and "mass produce" their product. Lesson fundamental understandings: Essential Questions: 1. Do I have any "leftovers" in my chemical process? If so, what is left? Can I rework my "recipe" to avoid these leftovers? 2. What is the % yield for my "recipe"? How do I have to adjust my recipe to make enough product? Standards National Standards Scientists conduct investigations for a wide variety of reasons. For example, they may wish to discover new aspects of the natural world, explain recently observed phenomena, or test the conclusions of prior investigations or the predictions of current theories. * Mathematics is essential in scientific inquiry. Mathematical tools and models guide and improve the posing of questions, gathering data, constructing explanations and communicating results. * Scientific explanations must adhere to criteria such as: a proposed explanation must be logically consistent; it must abide by the rules of evidence; it must be open to questions and possible modification; and it must be based on historical and current scientific knowledge. State Standards Nevada: 20.12.4 Compare groups of data, taking into account both percentages and actual numbers 22.12.1 Analyze experimental procedures and suggest appropriate revisions for improvement 23.12.2 Use algebraic equations when appropriate 23.12.5 Trace the source of differences between an estimate and the calculated answer that exceeds agreed-upon standards for precision 24.12.5 Write procedures for investigation of delegated or original scientific problems Lesson Prerequisite Skills Content Area Skills: 1. naming compounds and writing formulas 2. writing and balancing equations 3. determining molar mass of compounds 4. converting grams to moles and moles to grams Laboratory Skills: 1. massing chemicals with proper significant figures 2. using measuring tools 3. use of bunsen burner (some projects) 4. use of thermometers (some projects) 5. familiarity with basic safety rules and procedures Teacher Information/Situations/Setting/Time Class Activity and Guided/Independent Practice: 45 min Application Lab: 45 min Task #5 (Analysis & Mass Production of Product): 2- 45 min sessions Materials (Application Lab): Mixture of baking soda/salt; hot plates or bunsen burners, scales, crucible, crucible tongs, aprons, goggles Materials (Project): As written by students Resources: The Case of the Adulterated Baking Soda (CRYSTAL Lab); Burrito worksheet (attached) Pre-lesson preparation: 20 minutes to set up lab; make baking soda/salt mixture; Have students set up own lab for production of materials Assessment Guided/Independent Practice - student corrected Independent Practice - Homework Application Lab Quiz Task #5 Worksheet (attached) Student Activity/Tasks Warm-up: How many Burritos Will We Make? Guided/Independent Practice in class Independent Practice as Homework Application Lab Quiz Task #5 Lab Time (Mass Production of Product) Enrichment/Alternate Activity: Students may need additional practice problems or labs Students may need additional time to mass produce their product Cross-Curricular: Math - ratios and dimensional analysis Technology Requirements/Tools/Materials Overhead projector may be used for guided and independent practice Acknowledgements: Exploration lab came from: CRISTAL Program, Iowa Chemistry Task Force, University of Northern Iowa, Price Laboratory School, Dr. Jody Stone, Project Director Additional Resources Main URL: Related Lessons Related Resources Burrito Worksheet Chemicals - R - Us Step 5 Worksheet Mass Production Copyright © 1997-2003 Career Connection to Teaching with Technology USDOE Technology Innovation Challenge Grant Marshall Ransom, Project Manager All rights reserved.