Welcome to Chemistry 376

Transcription

1 CHM 376 Spring 2014 Welcome to Chemistry 376 This course will give you a chance to explore the experimental world of physical chemistry. In each of six experiments you will study how simple physical models, familiar to you from your lecture courses, correspond with your own real observations. Fundamental scientific knowledge comes to us via experiment, and you will establish yourselves as legitimate gatherers of such knowledge. Physical chemistry is the study of the underlying physical principles that govern the properties and behavior of chemical systems. As such, it is foundational to all other areas of chemistry. The field of physical chemistry traditionally is composed of three broad topics: (i) thermodynamics and statistical mechanics, (ii) quantum chemistry and spectroscopy, and (iii) kinetics and reaction dynamics. The experiments you will perform will touch on several of these areas, but is obviously far from comprehensive. During the first week of lab, you will familiarize yourself with some of the equipment, computers, and programs (LabView and Igor Pro) that will be used throughout the semester. The laboratory exercise involves a comparison of two different types of temperature sensors. The first two two-week experiments are based in thermodynamics. In experiment 2, you will measure the temperature drop experienced by different gases in a Joule-Thomson expansion. In experiment 3, you will measure the small differences between the enthalpy of binding of the first and last water molecules in CuSO 4-5H 2 O. In experiment 4, a kinetics experiment, you will measure the pressure and temperature dependence of the rate of a chemical reaction in the gas phase, and use the results to test a model for the reaction mechanism. The last two 2-week experiments make connection with the fields of quantum chemistry and spectroscopy. In experiment 5, you will measure the absorption spectra of a series of polyene dyes, and use these to test a quantum mechanical particle in a box model. In experiment 6, you will use Raman spectroscopy to measure the vibrational frequencies of various solutions and solids, and to study the effects of solvent on the vibrational frequencies. And finally, we will end with two one-week computer experiments. The first involves Ab initio calculations, where a reaction is studied utilizing the lowest energy states of the reactants and product. The second explores the AFM (atomic force microscope), a powerful tool in nanotechnology. Over the course of the semester, you will learn some useful modern instrumental methods. You will also see some of the subjects you first encountered in your lecture courses illuminated in much more detail. But most importantly of all, in this course you will have the opportunity to be creative, critical, quantitative observers of nature. Success in this pursuit is the thing that will be rewarded most. Organization of the Course The laboratory, which meets in WTHR , is divided into the following sections. Section Day Time 1 Mn 2:30-5:20 2 Tu 8:30-11:20 3 Tu 2:30-5:20 4 We 8:30-11:20 5 We 2:30-5:20 6 Th 8:30-11:20 7 Th 2:30-5:20 8 Fr 2:30-5:20 Contact Information Lab Coordinator: Paul Bower WTHR 173A pbower@purdue.edu Phone: We will all gather on Monday mornings at 8:30 in Room WTHR 320. This hour will be devoted to pre-laboratory lectures, chemistry tours and quizzes. A schedule for the semester is on the next page.

2 Chemistry 376 Lab and Lecture Schedule For each laboratory a written report will be prepared in your notebook as you do the experiment. This report will be turned in, in the form of duplicate pages, at the end of your section's lab time (See pages 4 & 5 for details). There will be three quizzes as shown, but no comprehensive Final Exam. Laboratory Monday 8:30 Lecture Week Experiment Date Lecture Subject Quiz Subject 1 Temp. Sensors and Computers Analysis 2 [MLK Jr. Day] No Lab!! Jan. 13 Jan. 20 Temp. Sensors and Computers Analysis [MLK Jr. Day] No Classes 3 Joule Thomson Jan. 27 Joule Thomson 4 Joule Thomson Feb. 3 Propagation of Errors 5 Heat of Reaction Feb. 10 Heat of Reaction 6 Heat of Reaction Feb. 17 Gas Kinetics 7 Gas Kinetics Feb. 24 QUIZ Joule Thomson & 8 Gas Kinetics Mar. 3 Group Presentations 9 Electronic Spectroscopy 10 Mar. 10 Electronic Spectroscopy [Spring Break] Mar. 17 [Spring Break] 11 Electronic Spectroscopy Heat of Reaction Mar. 24 QUIZ Gas Kinetics & Electronic Spectroscopy 12 Raman Spectroscopy Mar. 31 Raman Spectroscopy 13 Raman Spectroscopy Apr. 7 Group Presentations 14 Ab Initio Calculations Apr. 14 Ab Initio Calculations 15 AFM Module Apr. 21 QUIZ Raman Spectroscopy & Ab Initio Calculations 16 No Lab Apr. 28 No Lecture 2

3 Grading Laboratory Reports (3 x 50 pts. + 5 x 100 pts.) Quizzes given during lecture time (3 x 50 pts.) TA Evaluation of student s performance TOTAL POINTS DURING SEMESTER = 650 pts. 150 pts. 50 pts. 850 points Grade Cutoffs A: 730 pts. B: 645 pts. C: 560 pts. D: 475 pts. The above absolute grading scale makes it easy for you to estimate your grade at any point during the course; it also provides an incentive for working together, rather than competing for grades. NOTE: No make-up quizzes or labs will be given. No late laboratory reports will be accepted. Regrades of quizzes and labs must be done within 7 days of receiving them. Textbook Copies of Experiments in Physical Chemistry (5th Ed.) by Shoemaker, Garland and Nibler are available on reserve in the Chemistry Library and are also available in the P-Chem Lab (WTHR ). The book An Introduction to Error Analysis by John R. Taylor is on reserve in the chemistry library. You might find it useful to own this book, which can be purchased at amazon.com, among other places. Detailed handouts describing each experiment will be available in WTHR 173 the week before the start of the experiment. They will also normally be available in lab the previous week. Laboratory Notebook A quadrille laboratory notebook with duplicate numbered pages is required. Carbon copies of your day's observations analysis and conclusions will be turned in at the end of each of your laboratory periods. These pages will constitute the entirety of your laboratory report for each experiment. The general rule of thumb: Everyone will give the TA copies of all work done during the lab. Each lab group will give one copy of each graph made to the TA. Laboratory Safety While experiments in Chem 376 are not intrinsically dangerous, the possibility of accidents is ever present, so you should approach each experiment defensively. Handouts will contain safety notes, and your TA will watch for unsafe practices. If you have any doubt, stop, consider the consequences of your actions and/or consult a TA. You must wear eye protection while in the laboratory. Laboratory Reports For each laboratory exercise you will prepare a report within your laboratory notebook as you do the experiment. Your report will consist of an introduction and pre-lab questions, prepared before you come to lab, the raw data as you record it over the course of the experiment, its reduction to tabular and graphical results, and your conclusions and discussion. Each experiment will take two laboratory periods. You will turn in what you have in your notebook at the end of each period (as duplicate pages). These will be assembled at the end of the experiment and graded by your TA. So what constitutes an excellent lab report? The rule of thumb to remember is that a report should include everything necessary so that someone who has never been in the P-Chem lab could be able to 1) see all the raw data collected, and how it was collected; 2) easily see how the raw data was converted to useful quantities with equations, with sample calculations for each type of conversion; 3) see the results of these calculations with appropriate tables; 4) understand all graphs created, with an understanding of why these graphs were made and the information that is attained by these graphs; 5) see the calculated final results, and realize the importance of these results from the discussion. Your entries for each experiment should adhere to the following format: 3

4 1. Introduction. (20 pts) Before coming to lab you should write an introduction to the experiment you are about to perform. This will mainly be a statement of purpose, describing the idea or model you, as the experimenter, intend to test, and, briefly, how you intend to do it. For this section, as for all the ones following, you should use carbon paper so you produce a clear duplicate, which you will turn in as your report. Also included in the introduction section are your answers to the Pre-lab Questions, which should be placed just after your Introduction. This section is handed in to the TA at the very beginning of the lab period. **NOTE: You will lose points on the pre-lab questions if you are late for lab** 2. Experimental Data. (15 pts) At each step as you prepare to record new data, you should make note of the particular technique and procedure you are about to use. Then, in a tabular fashion appropriate to the experiment, you should simply write down your observations, including all the raw data you have collected as well as the apparatus that the data was collected from. The form you choose is up to you. Special neatness is not required, but your entries must be legible to your lab partner and your TA. 3. Data Analysis. (20 pts) Describe the theoretical models tested or the fundamental parameters extracted from your experimental results. This should include all the formulas you used to analyze your data, a description of how the calculation was performed, and a summary of the derived numerical results. Much of this analysis will be carried out on your laboratory computer. Make reference to those computations here, but still show a sample calculation, with units, for each type of calculation done. In some of the experiments, you will be combining your data with data collected by other groups in your laboratory section to obtain a more complete data set for error analysis. When required, this error analysis must be included in the report. 4. Graphical Presentation of Results. (10 pts) A well-composed graph is often the most informative way of summarizing the results of an experiment. In almost every case you will make these plots on your laboratory Macintosh computer. This should obviously have labeled axes (including units) and sufficient annotation to identify any lines or symbols used, as well as the experiment performed, the experimenters names, the date, and any other pertinent information. Make one copy of each graph per student plus one copy per group to turn into your TA. 5. Discussion and Conclusions. (35 pts) The discussion of your results and conclusions must be written in the lab during the last laboratory period for each experiment. You should begin by briefly summarizing your overall findings. Then reflect on the physical idea you sketched in the introduction. Do your results support this picture, or refute it, or are they inconclusive? A complete discussion should include some reference to related work found in appropriate textbooks (not CHM 370, 373/4 or 376 text books) and/or journal articles. This article must have been written within the last five years. Very useful journals include the Journal of Physical Chemistry and the Journal of Chemical Physics. This background reading should be done outside of the laboratory, before the last period for each experiment. Make a photo copy of the reference articles abstract (or first page), and include it with your lab report. NOTE: Under no circumstances are CHM 376 reports from past semesters permitted in the laboratory. 4

5 Policy on Submission of Laboratory Results Each of your laboratory reports will be submitted in parts at the end of each of the two laboratory sessions pertaining to each of our six experiments. No reports, or parts of reports, will be accepted outside of lab. The 2-Week Lab Rotation As can be seen from the Lab and Lecture Schedule, all of the labs (except the first & last two) are two-week labs. The following shows how these two-week labs are conducted. WEEK #1 MONDAY 8:30 : LAB Week 1 : LECTURE on topic of the lab to be performed --- Turn in Introduction with Pre-Lab Questions --- TA Lecture of Experiment (in WTHR 165A Lecture Room) --- Paul s Lab Equipment Lecture (in Lab) --- Collect LOTS of Data --- Make and Print Graphs --- Turn in Data page with 1 graph set / group At home, do all sample calculations (with units) for any calculation performed during the first week. Then, make a table displaying the results for all trials. Also, locate your reference article on a subject that relates to the current lab, and bring in the abstract or first page of the article to the lab to hand in with your final report. WEEK #2 MONDAY 8:30 : Weeks 6, 11 & 15: QUIZ on two recent Labs (50 points) Other weeks involve either extra lecture material or tours. LAB Week 2 : --- Quick TA Lecture --- Paul s Equipment Lecture on new stuff (in Lab) --- Collect Data & Make Graphs (~1.5 hours) --- WRITE LAB REPORT IN LAB and turn in (100 points) Group Presentations During weeks 8 & 13, we will have some of the students give oral presentations on their submitted articles that relate research to the experiments. These will be short 5-minute talks, and should include a minimum of three Powerpoint slides (which need to be ed to Paul Bower by 6 PM the Sunday before class). Groups will be created by volunteering, and each student can earn up to 10 extra credit points for their presentation. 5

6 5 WTHR Lecture Room Meet here before the lab starts. blackboard H a l l w a y WTHR Floor Layout of the Physical Chemistry Labs (WTHR ). There are five individual set-ups in each lab. We will meet in the lab lecture room between the labs. *** If the doors are unlocked, come on in! *** 6