Kinetic Theory. Governing Rules Series. Instructor s Guide. Table of Contents

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1 Kinetic Theory Governing Rules Series Instructor s Guide Table of Introduction When to Use this Video Learning Objectives Motivation Student Experience Key Information Video Highlights Video Summary Chem 101 Materials Pre-Video Materials Post-Video Materials Resources Chem 101 Intro CONTENTS Additional Resources Going Further References Appendix.... A1 Developed by the Teaching and Learning Laboratory at MIT for the Singapore University of Technology and Design Page 1 +

2 Introduction When to Use this Video Learning Objectives In Chem 101, at home or in recitation, after Lecture #20: Ideal gas law Prior knowledge: kinetic theory of gases After watching this video students will be able to: Motivation Student Experience Discuss the physical significance of a gas molecule s mean free path. Discuss the physical parameters that affect the mean free path. Kinetic theory provides important scaffolding for student understanding of the behavior of molecules. The assumptions of kinetic theory are frequently introduced in isolation without any opportunities for students to invoke them in real-world problem solving. It is highly recommended that the video is paused when prompted so that students are able to attempt the activities on their own and then check their solutions against the video. During the video, students will: Brainstorm questions and ideas they have related to the problem of light bulb blackening. Apply their knowledge of kinetic theory to explain light bulb blackening. Consider factors that affect collision frequency. Key Information Duration: 11:23 Narrator: Prof. Jeff Grossman Materials Needed: Think about what properties may be important for a gas used to fill a light bulb. Resources Chem 101 Intro INTRO Page 2

3 Video Highlights This table outlines a collection of activities and important ideas from the video. Time Feature Comments 1:39 The problem of light bulb blackening is introduced to students. 2:30 An animation is used to go over the basic anatomy of an incandescent light bulb. 3:42 The assumptions of kinetic theory are reviewed. 4:57 The connection between light bulb blackening and kinetic theory is made explicit to the students. 5:26 The concept of mean free path is introduced. After hearing about the problem, students are prompted to think about things that might be relevant to the problem. This should be a review for students. The video goes through a derviation for an approximate calculation of mean free path. Students then use this to think about what light bulb parameters they might change in order to decrease light bulb blackening. 6:56 Relative velocity calculation See Post-Video Materials #4 8:37 An animation explains the localized blackening that is seen in incandescent light bulbs used today. 9:39 Students hear how Irving Langmuir worked on the problem of light bulb blackening. Resources Chem 101 Intro INTRO Video Summary This video encourages students to access their knowledge of kinetic theory and apply it to the realworld problem of light bulb blackening. Students are also introduced to the concept of mean free path. Page 3

Chem 101 Materials Pre-Video Materials When appropriate, this guide is accompanied by additional materials to aid in the delivery of some of the following

Gas Concepts Review (Appendix A1) This clicker question, adapted from Nurrenbern and Pickering (1987) (see Reference list), will help students review basic gas

Gas Concepts Review (Appendix A2) This clicker question, adapted from Cornely-Moss (1995) (see Reference list), points to the idea that the atoms in the smaller

Gas Concepts Review (Appendix A3) These true/false questions are from Cornely-Moss (1995) (see Reference list).

4 Chem 101 Materials Pre-Video Materials When appropriate, this guide is accompanied by additional materials to aid in the delivery of some of the following activities and discussions. 1. Gas Concepts Review (Appendix A1) This clicker question, adapted from Nurrenbern and Pickering (1987) (see Reference list), will help students review basic gas concepts. This question checks for student understanding of gas behavior, that gases occupy the entire volume of a container. 2. Gas Concepts Review (Appendix A2) This clicker question, adapted from Cornely-Moss (1995) (see Reference list), points to the idea that the atoms in the smaller container will collide with the walls of their container with a higher frequency. 3. Gas Concepts Review (Appendix A3) These true/false questions are from Cornely-Moss (1995) (see Reference list). The first true/false question emphasizes the difference between average behavior and individual behavior. The root mean square speed of He is 926 mls at 27 o C, but every He atom does not have this speed. The second true/false question reviews the idea that rms speed is inversely proportional to mass. Resources Chem CHEM 101 Intro The third true/false question emphasizes that temperature is a measure of the kinetic energy of the atoms or molecules of a gas. Page 4

clothesline take longer to dry in a humid environment compared to a dry environment. 2.

theory and what they learned in the video to explain why. 3.

argon-filled incandescent bulbs. For homework, have students do some research and then explain why.

significance keeping in mind kinetic theory. 4.

5 Post-Video Materials 1. In small groups, have students use their knowledge of kinetic theory to discuss why clothes on a clothesline take longer to dry in a humid environment compared to a dry environment. 2. The video mentions that krypton and xenon may be more effective fill gases for incandescent light bulbs than argon. First in small groups, and then as a class discussion, have students use what they know about kinetic theory and what they learned in the video to explain why. 3. Tungsten halogen light bulbs use a tungsten filament but last longer and stay cleaner than argon-filled incandescent bulbs. For homework, have students do some research and then explain why. They should compare and constrast the design specifications of the two bulb types and explain their significance keeping in mind kinetic theory. 4. Relative velocity calculation The video quickly goes through a calculation of average relative velocity (the average velocity of a molecule relative to another molecule in the system). Be sure to go over this calculation with students or have them go over it for homework so that they understand where the square-root of 2 in the calculation of mean free path comes from. Resources Chem CHEM 101 Intro Page 5

6 Additional Resources Going Further Diffusion is a nice follow-up application of kinetic theory. The Gradient Concept Vignette covers this topic well. Davidson University s Virtual Chemistry Experiments website (reference below) provides simulations showing the displacement and random walk of a tracer molecule diffusing. References The following website provides a nice overview of kinetic theory, including a simulation of diffusion. Blauch, D. N. (2009). Virtual Chemistry Experiments: Kinetic Molecular Theory of Gases. Retrieved from The following papers highlight student difficulties with kinetic theory and provide additional resources for in-class discussion questions. Cornely-Moss, K. (1995). Exam Question Exchange. Kinetic Theory of Gases. Journal of Chemical Education. 72(8), Nurrenbern, S. (1987). Concept Learning versus Problem Solving: Is There a Difference? Journal of Chemical Education. 64(6), Plumb, R. C. (1975). Chemical Principles Exemplified. Light Bulbs Filled with Krypton Gas. Journal of Chemical Education. 52(6), The following book provides interesting and detailed information about Irving Langmuir s work on the incandescent light bulb. Suits, C. G., Way, H. E. (Eds.) (1960). Heat Transfer - Incandescent Tungsten: Vol. 2. The Collected Works of Irving Langmuir. New York: Pergamon Press. The following MIT Open CourseWare lecture addresses kinetic theory. Resources RESOURCES Chem 101 Intro Cummins, Christopher, and Sylvia Ceyer Principles of Chemical Science, Fall (Massachusetts Institute of Technology: MIT OpenCourseWare), (Accessed 10 Mar, 2012). License: Creative Commons BY-NC-SA Video Lecture #13 discusses kinetic theory. Page 6

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Entropy. Governing Rules Series. Instructor s Guide. Table of Contents

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