Ideas, Concepts, and Applications of Quantum Mechanics

Transcription

1 Unit: 13 Lesson: 01 Suggested Duration: 5 days Ideas, Concepts, and Applications of Quantum Mechanics Lesson Synopsis: This unit opens with the simple question: What is matter made of and how is it put together? This question leads to quantized energy packets (photons) and the ideas that an electron and other particles have wave properties. Concepts are presented from a historical point of view with a focus on the critical experiments and scientists contributions to the topic. The Bohr model of the hydrogen atom and quantized energy levels provide a powerful model with new and useful concepts applied. TEKS: P.5 Science concepts. The student knows the nature of forces in the physical world. The student is expected to: P.5A P.5H Research and describe the historical development of the concepts of gravitational, electromagnetic, weak nuclear and strong nuclear forces. Supporting Standard Describe evidence for and effects of the strong and weak nuclear forces in nature. Supporting Standard P.8 Science concepts. The student knows simple examples of atomic, nuclear, and quantum phenomena. The student is expected to: P.8A P.8B P.8C P.8D Describe the photoelectric effect and the dual nature of light. Readiness Standard Compare and explain the emission spectra produced by various atoms. Supporting Standard Describe the significance of mass-energy equivalence and apply it in explanations of phenomena such as nuclear stability, fission, and fusion. Supporting Standard Give examples of applications of atomic and nuclear phenomena such as radiation therapy, diagnostic imaging, and nuclear power and examples of applications of quantum phenomena such as digital cameras. Supporting Standard Scientific Process TEKS: P.2 Scientific processes. The student uses a systematic approach to answer scientific laboratory and field investigative questions. The student is expected to: P.2F P.2J P.2K Demonstrate the use of course apparatus, equipment, techniques, and procedures, including multimeters (current, voltage, resistance), triple beam balances, batteries, clamps, dynamics demonstration equipment, collision apparatus, data acquisition probes, discharge tubes with power supply (H, He, Ne, Ar), hand-held visual spectroscopes, hot plates, slotted and hooked lab masses, bar magnets, horseshoe magnets, plane mirrors, convex lenses, pendulum support, power supply, ring clamps, ring stands, stopwatches, trajectory apparatus, tuning forks, carbon paper, graph paper, magnetic compasses, polarized film, prisms, protractors, resistors, friction blocks, mini lamps (bulbs) and sockets, electrostatics kits, 90-degree rod clamps, metric rulers, spring scales, knife blade switches, Celsius thermometers, meter sticks, scientific calculators, graphing technology, computers, cathode ray tubes with horseshoe magnets, ballistic carts or equivalent, resonance tubes, spools of nylon thread or string, containers of iron filings, rolls of white craft paper, copper wire, Periodic Table, electromagnetic spectrum charts, slinky springs, wave motion ropes, and laser pointers. Organize and evaluate data and make inferences from data, including the use of tables, charts, and graphs. Communicate valid conclusions supported by the data through various methods such as lab reports, labeled drawings, graphic organizers, journals, summaries, oral reports, and technology-based reports. P.3 Scientific processes. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions within and outside the classroom. The student is expected to: 2012, TESCCC 01/22/13 page 1 of 11

2 P.3A P.3D In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student. Explain the impacts of the scientific contributions of a variety of historical and contemporary scientists on scientific thought and society. GETTING READY FOR INSTRUCTION Performance Indicator(s): Create an informational brochure to describe the structure of atoms and the photoelectric effect. In the brochure, include a description of how line spectra from gases are produced and analyzed and the quantum mechanical concepts (wave and particle nature of light). Additionally, include information on the history of nuclear physics, including persons, nuclear stability, nuclear energy, and uses in energy and therapy. (P.2K; P.3D; P.5A, P.5H; P.8A, P.8B, P.8C, P.8D) 4G; 5F Key Understandings and Guiding Questions: Classical (continuous) models of matter do not correctly describe matter and energy at the atomic level and below. As matter is broken into smaller and smaller chunks, what do we find? The Bohr model of atoms consists of a heavy positive nucleus with electrons in planetary-like motion in specific orbits around the nucleus with specific energies. The spectra from these atoms are described by quantum mechanical ideas. If an atom resembles a planetary system, why does the light given off consist of only specific wavelengths? What is meant by quantized, and why are some things quantized at the atomic level? The nucleus also has an internal structure and is composed of protons and neutrons held together with nuclear forces. If the ratio of neutrons to protons is wrong, the nucleus is unstable and radioactive. Does the nucleus have an internal structure? What keeps the protons from repelling away from each other? What is radioactivity? E=mc 2 describes the conversion of mass to energy, which occurs in fission and fusion processes. Why are nuclear energies comparatively large? How is mass converted to energy? Atomic and nuclear effects (quantum mechanical theories) have led to useful applications. Is there any practical application of studying the atom or nucleus? Vocabulary of Instruction: quantum photon de Broglie wave length energy level transition Planck s constant laser atomic lifetime atomic transition wave-particle duality uncertainty principle line spectra isotope metastable state photoelectric effect 2012, TESCCC 01/22/13 page 2 of 11

3 black body radiation Bohr model of the atom correspondence principle excited state ground state probability coherent light electromagnetic spectrum Rutherford Scattering radioactive fission stimulated emission wave function radiation therapy unstable uncertainty principle fusion 2012, TESCCC 01/22/13 page 3 of 11

4 Materials: Refer to the section for materials. Attachments: Handout: Anatomy of Physics (1 per student ) Handout: History of the Atom Notes (1 per student) Teacher Resource: History of the Atom Notes KEY Teacher Resource: Suggestions for Atom Video Handout: Evidence for the Bohr Model of the Atom (1 per student) Handout: VQM-Spectra Lab (1 per student) Teacher Resource: VQM-Spectra Lab KEY Handout: Particles and Waves Notes (1 per student) Teacher Resource: Particles and Waves Notes KEY Teacher Resource: Suggestions for Particles and Waves Video Teacher Resource: He-Ne Laser Simulation Handout: Helium Neon Laser (1 per student) Teacher Resource: Helium Neon Laser KEY Handout: Nuclear Forces, Stability, and Energy (1 per student) Handout: Student Investigation (1 per student) Teacher Resource: Student Investigation KEY Handout: Critical Events of Quantum Mechanics (1 per student) Resources and References: Video: Annenberg Video Index: (The Atom, Number 49) Video: Annenberg Video Index: (Particles and Waves, Number 50) Simulation: Emission Spectroscopy: Website: Phet Lasers: Advance Preparation: 1. Prior to Day 1, install and test the Internet simulation and videos. 2. Practice the projection and time manipulation of the Annenberg films prior to class. This site allows you to stream the videos used in this lesson. In the study of thermodynamics, you may have registered to use this site. Two videos are used in this unit, and you will need to make sure that you have access on demand. Review the suggestions for viewing the videos in order to reduce class time required. 3. Prepare attachment(s) as necessary. Background Information: This unit bundles student expectations that examine the history and applications of quantum mechanics as it relates to atomic structure, the photoelectric effect, and line spectra. 2012, TESCCC 01/22/13 page 4 of 11

5 Prior to this unit, students have had little exposure to quantum mechanics. Students have explored matter and energy and the relationship between the different forms of energy. During this unit, students will investigate the topics of mass to energy conversion, radioactivity and nuclear stability, and commercial uses of nuclear power and medicine. This is the final unit that will connect these topics and give students a deeper understanding of their applications in science. The material in this unit is presented from a historical point of view which helps to explain how it was developed and where its application is necessary. The conservation principles of classical physics have proved invaluable in making sense of the information and provided a foundation from which to build new theories and explain the applications resulting from quantum knowledge, such as lasers, microelectronics, super conductors, medical instrumentation, and weapons. There are even implications for philosophy. STAAR Note: The concepts and skills explored in this unit will address standards associated with the STAAR Physics assessment, Reporting Category 4: Waves and Quantum Phenomena. GETTING READY FOR INSTRUCTION SUPPLEMENTAL PLANNING DOCUMENT Instructors are encouraged to supplement and substitute resources, materials, and activities to differentiate instruction to address the needs of learners. The Exemplar Lessons are one approach to teaching and reaching the Performance Indicators and Specificity in the Instructional Focus Document for this unit. Instructors are encouraged to create original lessons using the Content Creator in the Tools Tab located at the top of the page. All originally authored lessons can be saved in the My CSCOPE Tab within the My Content area. INSTRUCTIONAL PROCEDURES ENGAGE/EXPLORE Ideas, Concepts, and Applications of Quantum Mechanics 1. Distribute the Handout: Anatomy of Physics to each student. 2. Review the areas that have been addressed so far in the course, down to atomic physics and quantum mechanics. 3. Inform students that just as strange things happened at very high speeds (relativity), the world of atoms is smaller and unusual as well. 4. Inform students that the physics ideas developed to explain the atom are the gateway to the other subject areas of solid state physics, nuclear, and fundamental particles. 5. Inform students that they will be developing an informational brochure of materials for this lesson, so they should keep the handouts and their notes in their science notebooks. 6. Facilitate a discussion using the following questions to review the atomic model: What do you get when you break matter into smaller and smaller chunks? Is there a smallest amount of a substance that will still be that substance? (An atom or molecule is the name we give to it.) What do you get if you break an atom into parts? (Neutrons, protons, and electrons) Do atoms have photons inside of them? (This question is to generate student thinking. The model indicates they are created during the electron transition.) NOTE: 1 Day = 50 minutes Suggested Day 1 Materials: classroom computer with Internet and display Attachments: Handout: Anatomy of Physics (1 per student) Handout: History of the Atom Notes (1 per student) Teacher Resource: History of the Atom Notes KEY Teacher Resource: Suggestions for Atom Video Instructional Notes: The purpose of today is to introduce the quantum mechanics unit. This historical approach depends heavily on the Annenberg film, the Atom. Viewing the film, along with comments following the film, will require minutes so the introductory activities should be monitored closely for time. 2012, TESCCC 01/22/13 page 5 of 11

6 What are photons? What are particles or waves? What are the characteristics of waves and of particles? (The questions are meant to remind students: waves undergo interference and are spread out and particles have mass and are localized (have a location). Photons have characteristics of both.) 7. Say: The topic of this unit is quantum mechanics. What is a quantum? What does it mean that something is quantized? Accept all answers at this time. A quantum is a bundle; pixels are bits of a picture; stairs are quantized, ramps are not; some things are quantized when you get to the details; and a charge comes in quanta of the electron charge. All charge is a multiple of the charge of an electron. 8. Two topics should be addressed quickly before showing the video. This will assist in the understanding of physics principles that are important to understanding the history of atomic theory. Electromagnetic wave formation by accelerated charges Maxwell s theory. Any charged particle radiates electromagnetic radiation when accelerated. This is how the theory of light was developed by Maxwell and is an important cornerstone of e-m theory. The video, The Atom, gives a history of the Bohr model of the hydrogen atom but it is part of a series that tends to reference, indirectly, earlier videos or other information that your students may not have. In addition, it quickly presents equations and occasionally presents concepts using calculus. Suggestions for viewing the video appropriately are included in the Teacher Resource: Suggestions for Atom Video. Annenberg Video Index: html?pid=619 (The Atom, Number 49) Science Notebooks: Students keep notes in their notebooks to use in the upcoming informational brochure. Note that light is electromagnetic radiation, and as heated things get hotter and glow, the dominant color changes from red to yellow to white to blue-white, going toward shorter wavelengths. Classical theory indicated much more ultraviolet radiation than is found in reality. The puzzle was solved by assuming E = hf, that the energy of light depends upon its frequency or wavelength. Maxwell was the dominant theoretical physicist on electricity and magnetism and explained that accelerating charges produced electromagnetic radiation. (Recall that radio waves are produced by forcing electrons up and down an antenna.) Black body radiation The video mentions this topic briefly, and it is explained in the next video but a quick preview provides context for the discussion. 9. Provide the Handout: History of the Atom Notes to students, and ask students to take notes on the handout. 10. View relevant portions of the video, The Atom, at the following website: Annenberg Video Index: pid=619 (Number 49). Use the Teacher Resource: Suggestions for Atom Video to provide suggestions for using the video efficiently. 11. Instruct students to answer the questions on the Handout: History of the 2012, TESCCC 01/22/13 page 6 of 11

7 Atom Notes and keep it for future reference. EXPLORE/EXPLAIN Energy Level Diagrams and Atomic spectra Suggested Day 2 Bohr Model of the Atom Introduction: 1. Remind students that in studying electrostatics, we gave evidence for the atomic model of matter and that the video yesterday extended and gave more detail. 2. Distribute and briefly discuss the Handout: Evidence for the Bohr Model of the Atom. 3. Remind students of the following: In studying waves, we were able to identify atoms by their characteristic spectrum. Now, we know that these colors result from jumps between energy levels (orbits). The size of the orbit determines the energy of the atom with the electron in that orbit. There is a direct correspondence between each electron orbit and the energy of the atom. Students may also remember the hydrogen spectral lamp and the spectra activity of identifying elements in stars. 4. Provide students with the Handout: VQM - Spectra Lab, and discuss the investigation, located at the following site: Emission Spectroscopy: 5. Demonstrate how to add energy levels, move them around, and make transitions. 6. Monitor and assist as necessary. 7. When students are finished, facilitate a post-lab discussion: Ask: If an atom resembles a planetary system, why does the light given off consist of only specific wavelengths? (Because the electron will release energy in the form of light at a specific wavelength to move back to another energy level) 8. Instruct students to record their answers in their science notebooks and keep their lab copy to use for the performance assessment at the end of the lesson. Materials: access to student computers with Internet Attachments: Handout: Evidence for the Bohr Model of the Atom (1 per student) Handout: VQM - Spectra Lab (1 per student) Teacher Resource: VQM - Spectra Lab KEY Instructional Notes: The goal for today is to review and expand the Bohr model of the hydrogen atom and other atoms. The evidence for this model is reviewed, including the importance of the atomic spectra from various atoms as a unique finger print. Planck s equation relating the energy of a photon to its frequency or wavelength is expanded including the reintroduction of electron volt energy units which are commonly used in these discussions. Simulations and problems provide detailed experiences for the student. STAAR Note: This lesson addresses standards associated with Waves and Quantum Phenomena. Misconceptions: Students at almost all levels have understanding difficulties and 2012, TESCCC 01/22/13 page 7 of 11

8 misconceptions about atoms and molecules. Some students may think the word nuclear always refers to atomic bombs. Science Notebooks: Students summarize notes in their notebooks. EXPLORE/EXPLAIN Particles, Waves, and Uncertainties Suggested Day 3 Concept of Particle-wave Duality Introduction: 1. Facilitate a class discussion with the following questions. Ask: A photon has wave and particle properties, but what about electrons; what are they particle or wave or both? (The electron is both.) What evidence is there that electrons have wave properties? Can it make interference patterns? That is what we will find out today and tomorrow, so do not reveal the answer at this time. (The answer is yes.) Why are the orbits of the hydrogen atom quantized? Where have we seen this behavior before? Hint: standing waves (Yes, we found that the frequencies for standing waves were quantized. We did not use that language, but only certain wavelengths and frequencies produced standing waves for a given situation.) 2. Distribute the Handout: Particles and Waves Notes to students, and view the video Particles and Waves from the Annenberg film series, website: Annenberg Video Index: number 50. The Teacher Resource: Suggestions for Particles and Waves Video provides some suggestions for using the video efficiently. 3. Students should follow the film, answering questions on the Handout: Particles and Waves Notes as the topics unfold in the film. You may wish to pause the video and discuss to allow students time to record notes. 4. Discuss the questions on the Handout: Particles and Waves Notes related to the film, and clarify any missing information or misconceptions. Note: The last section in the student handout summarizes material covered very quickly in the film, but that should be reviewed by the teacher. Materials: classroom computer with Internet and display Attachments: Handout: Particles and Waves Notes (1 per student) Teacher Resource: Particles and Waves Notes KEY Teacher Resource: Suggestions for Particles and Waves Video Instructional Notes: The goal for today is to examine the wave-particle duality concept of matter and, to the degree possible, introduce some of the concepts of wave mechanics or quantum mechanics. The results of calculations in Quantum Mechanics often result in probabilities of various results which are accurate in the whole since the number of particles is almost always very large. The average value predictions of the probabilities agree with measurements. As disturbing as it might be to think of light as being both a wave and particle, for many it is even more disturbing to think of matter (particles) as being both a particle and a wave. In reality, several prominent thinkers (Einstein and others) reject the interpretation (meaning) of some of the calculations. They reject the language, 2012, TESCCC 01/22/13 page 8 of 11

9 but fully agree that the calculations describe or predict the reality of measurements. The video shown today is the next one in the series following the video, The Atom, from Annenberg s Mechanical Universe and Beyond. It continues the historical development of quantum mechanics and hints at some of the controversy of interpretation. Note: In any event, the mathematical formulation details are well beyond the scope of this course and the film simply highlights some of the interesting conclusions. Students are expected to answer questions related to the content of the film on a handout designed for that purpose. Science Notebooks: Students keep notes and handouts in their notebooks for use in preparing the Performance Indicator. ELABORATE Lasers and Nuclear Theory Suggested Day 4 Examination of LASER Principles as an Elaboration of Atomic Theories (15 20 minutes): 1. Inform students that today will be spent on two topics - lasers and nuclear physics. 2. With the Phet simulation of the He-Ne laser displayed and set as indicated on the Teacher Resource: He-Ne Laser Simulation, provide the Handout: Helium Neon Laser to students. This handout serves as discussion notes for the students and has questions to be answered. Website: Phet Laser Simulation: 3. Discuss the document emphasizing that the LASER words tend to explain how the device works when the terms are explained. 4. Use the simulation to demonstrate the terms and how they relate to the laser components. The energy level diagram for He and Ne can be confusing, but emphasize the importance of the metastable state to hold the electron Materials: classroom computer with Internet and display Attachments: Teacher Resource: He-Ne Laser Simulation Handout: Helium Neon Laser (1 per student) Teacher Resource: Helium Neon Laser KEY Handout: Nuclear Forces, Stability, and Energy (1 per student) Handout: Student Investigation (1 per student) Teacher Resource: Student 2012, TESCCC 01/22/13 page 9 of 11

10 in place for stimulated emission. 5. Following the discussion/demonstration, assist the students in answering the questions at the end of the handout. Nuclear Principles of Radioactivity and Nuclear Energy Introduction (20-25 minutes): 1. Provide students with the Handout: Nuclear Forces, Stability, and Energy. Instruct student to use the handout as notes as the topics in the handout are discussed. 2. Discuss the importance of understanding why the nucleus of an atom becomes radioactive. As a check for understanding, ask students the following: Does the nucleus have internal structure? (Yes, the nucleus contains subatomic particles (protons and neutrons) that have mass, and the protons are positively charged.) What keeps the protons from repelling away from each other? (Nuclear forces) What is radioactivity? (The instability of the nucleus due to the imbalance of the subatomic particles) Why are nuclear energies relatively large? (Because of the nuclear forces) How is mass converted to energy? (Through the process of nuclear fission) Investigation KEY Handout: Critical Events of Quantum Mechanics (1 per student) Check for Understanding: Students research of applications of modern physics technology provides an opportunity for formative assessment. Instructional Notes: The LASER is studied as an application of quantum mechanical and atomic physics theories, followed by a brief overview of basic nuclear physics ideas and principles. The laser presentation follows a demonstration format with a Phet simulation. Science Notebooks: Students keep notes and handouts in their notebooks for use in preparing the Performance Indicator. Research Assignment on Modern Physics Applications: 1. Ask: Are there any practical applications of studying the atom or the nucleus? (Yes, it has provided us with multiple applications in technology, energy, medicine, and communication.) 2. Provide the Handout: Student Investigation to students, and explain that they are to provide examples and/or otherwise explain how modern physics has provided technology for our daily lives. Note: Using the Internet is the simplest way to obtain this information, but other sources may be allowed. 3. Distribute a copy of the Handout: Critical Events of Quantum Mechanics to each student, and review with students. EVALUATE Performance Indicator Suggested Day 5 Performance Indicator Create an informational brochure to describe the structure of atoms and the photoelectric effect. In the brochure, include a description of Materials: 2012, TESCCC 01/22/13 page 10 of 11

11 how line spectra from gases are produced and analyzed and the quantum mechanical concepts (wave and particle nature of light). Additionally, include information on the history of nuclear physics, including persons, nuclear stability, nuclear energy, and uses in energy and therapy. (P.2K; P.3D; P.5A, P.5H; P.8A, P.8B, P.8C, P.8D) 4G; 5F 1. The format of the brochure may vary with the conventions of a particular school or classroom, but it should have some theme or sense of organization. For example, it could follow the timeline in which materials were collected, or it could be sectioned into history, theory, lab activities, and other. 2. Students may use technology to create the brochures (if available). For example, Word has brochure templates available. paper markers and/or colored pencils access to student computers with Internet (optional) previously distributed handouts and notes from the lesson Science Notebooks: Students keep notes and handouts in their notebooks for use in preparing the Performance Indicator. 2012, TESCCC 01/22/13 page 11 of 11