CH302 Random Musings April 1, 2008—All the Extra Credits 1. The exam scores for exam 2, before correction for problems being tossed, were a 76 and a 66. Pretty much as I expected. The score of 76 was excellent, the highest in the history of the equilibria/electrochemistry exam in this course, and It will go higher with problems being tossed. 2. I have promised to throw out unfair problems and appreciate the suggestions that you all have made. I met with VandenBout and we discussed various problems and for the first exam, there are at least three being removed. We are now looking at exam 2 and will make a decision by Thursday. On Thursday I will have a musings and mention which questions are being tossed for every exam and quiz this semester. 3. And of course this is where I remind you to never give up. Many of you came to see me in preparing for the second exam after struggling on the first—some did much better. Some are still getting used to how to do well on this kind of exam. But you have to keep after it. All it takes is getting everything under control and in your head for just one glorious 3 hour period during the final exam in May, and you can have you’re a as well. 4. We are on to kinetics so as we start, here is an example of kinetics from my own life involving kinetics: Dave figures out how to save hundreds of dollars on potatoes using kinetics. I shop at WalMart for groceries because they are so darn cheap. Consequently I end up being able to buy a 10 pound bag of potatoes for the cost of a 5 pound bag elsewhere. The problem is that I don’t like making mashed potatoes every night of the week, so the potatoes end up sitting around. Before I know if, they have grown those nasty tentacles, which are so disgusting I end up throwing the potatoes away. Like clockwork, every second week, boom, five pounds of tentacled left-over potatoes tossed—I might as well be shopping at Randalls. Then one day I remembered my kinetics and how maybe all that stuff about rates of reactions of chemicals applied to potatoes as well. I stuck a bag of potatoes in the refrigerator in the garage, and have kept it there for 3 months— no tentacles at all. The only problem is that they are in the garage so I forget I have them and the rate of eating mashed potatoes has gone way down as storage time has soared. 2 months in a refrigerator --yummy mashed potatoes 2 months in the pantry--too gross for words The data: Day tentacle length (78oF) tentacle length (35oF) 1 0 0 2 0 0 3 0 0 4 0 0 5 2 0 6 3 0 7 5 0 8 7 0 Rate of tentacle growth between days 7 and 8: (35oF) 0 mm per day = (0-0)/(8-7) (78oF) 2 mm per day = (7-5)/(8-7)5. A bit of advice on what makes kinetics so challenging. In a word: vocabulary. Unlike acid base equilibrium where I spent 2 months teaching you how to reduce the problems to simple common forms like A--or BH++, the material in kinetics is very broadly covered and involves concepts that will be unfamiliar even to people who had a lot of chemistry in high school. And to top it off, look at why is all seems like such a blur as you consider trying to distinguish the following phrases from one another: • Rate • Rate expression • Rate Constant • Differential Rate Law • Integrated Rate Law • Method of Initial Rates • Rate Determining Step Very simply, if you can’t explain EXACTLY how each of these is defined, you can’t solve kinetics problems. 6. Oh, and here are the question types for quiz 5 next Thursday: • assigning rate expressions • method of initial rates • identifying order of reaction from rate constant • Arrhenius calculation • integrated rate law calculation • half life calculation • kinetic theory--collision and transition state concepts • reaction mechanism 7. Extra Credit assignments and your course grade. No, I don’t curve. But as mentioned, I will be offering three extra credit opportunities in this class, each worth 1% of your grade. This is what I do rather than “curving” because I am sure that no one in here wants to get a grade they haven’t earned. So here are the details on earning your 3 extra credit. Procedures for turning in extra credits all follow the extra credit process used for Extra Credit 1--you must follow these in order to get the points--please don't make my life difficult by not doing what you are told. Procedure: • Complete the extra credit task below. • Write it up (probably 100 words or so, but write as much as you want to tell the story.) • Submit it as plain text in the body of the e-mail (no attachments!!) • Send it to [email protected] by the deadline • Jump for joy at having earned 1% of your course gradeExtra Credit Assignment 1: • Title: Spring break extra credit with your uteid appended (If you do not use this subject you will not be filtered into the file from which I assign extra credit.) • Due Date: Friday March 28 at noon. Instructions. During spring break I want you to teach a science-hater something interesting about chemistry that you have learned in this class. To get the points, the person you teach has to say to you, “gee, I had no idea chemistry was that interesting” when you have finished (you can make them say it even if they don’t mean it.). You can choose what you teach but I would recommend that it be something of interest and utility, like the complications of cooking at high altitude if you happen to be skiing at spring break or why fish explode if you happen to be at the beach, or why South Park was wrong or the value of adding salt to water to boil your pasta or why you shouldn’t add pure antifreeze to your car or why water balls up on windshields or how neutral water isn’t always pH 7 and on and on. It is your choice. Extra Credit Assignment 2: • Title: Undergraduate Research with your uteid appended (If you do not use this subject you will not be filtered into the file from which I assign extra credit.) • Due Date: Saturday May 3 at 3 am Instructions. Go to the undergraduate poster session on Friday, April 18th, some time between 11 am and 3 pm in the Welch Foyer (right outside this classroom.) For details, see: http://cns.utexas.edu/current_students/research/forum.asp Find a poster you like, talk to the person standing in front of it for 5 minutes, and then going home and email me about your experience. Spend a few sentences telling me who did the poster, why you liked the poster and
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