At the beginning of the quarter, Barr seemed to be an understanding and lenient professor. As the quarter went on, this quickly proved to not be the case. He constantly spews about how "empathetic" and "understanding" he is about being a student, especially since he just finished his PhD, yet then immediately turns around does the exact opposite of everything he claims. There are no alternate exam times, so all international students get is a crappy night's sleep and a half-assed "I'll factor this into the final grade" from Barr. The way he defended himself made it seem like it was a departmental policy to host live exams, yet the previous quarter with Felker proved this was clearly not the case as Felker even provided alternate times, so the only possible conclusion is that this was purely Barr's decision. Additionally, discussion sections are mandatory, screwing over international students even further if they don't get a good time during the rat-race that is UCLA course registration.

Besides lack of consideration for internationals, Barr institutes a load of arbitrary rules that only serve as obstacles to student learning. During discussion, we are forced to make groups to work on worksheets, homework, group exams, etc. However, Barr insisted that the groups be capped at 3 people and would forcibly break apart groups of 4 or more, despite this being completely online anyways. We are college students, not toddlers, which is why I do not see the point of mandatory group assignments especially on a Zoom environment. Fortunately, I landed a good group and we were able to get along well, but for those who preferred to work alone or got a poor group, they were stuck for the entire quarter.

Barr gives students loads of seemingly useful resources in the form of additional textbook problems, OWL reading quizzes, optional problem sets, all that were supposed to mimick his exams and homeworks: only half of that is true. Homework sheets were pulled from the problem sets, but exam questions were tangentially related at best. But, Barr claims that because his exam questions come from the Psets, he will not give answer keys! As a result, if you did decide to do the psets, the only way to check your work would be to match answers with other students, or go in for office hours. Regarding office hours, you can either go in for Barr's personal ones, where he would spend 40 minutes using his "socratic method", which you can read as "basically not answering the question". Or, you can do a TA's, but they aren't given answer keys either, and I have had times when the TA told us "yeah I'm not sure about this either." It took 7 weeks and loads of student (and probably TA) outrage before Barr finally relented and gave keys to the TAs, but sometimes they would be incomplete! This happened for the final psets leading up to finals week. You can imagine the frustration.

Lectures were moderately useful? He doesn't spend a lot of time on concepts, so hopefully you can get through the walls of dense that is Oxtoby, but his explanations are clear and he builds time for questions. The example problems he does are the only parts worth listening to. Originally he tried to do derivations, but those were often poorly motivated and a complete abuse of notation (for the more mathematically-minded folks). I guess he realized the derivations weren't helpful since he stopped after the first midterm.

There's quite a few gimme points which is probably the only reason I ended up with a passable grade. The only note is that you need to keep on top of all his surveys, reading quizzes, etc to really get the most out of them.

Lastly, grading, arguably one of the most important aspects of a course for students. Our midterms had two components: individual and group. Barr told us at the beginning of the quarter to allow for a week to grade. Our first group midterm (worth 20% of the midterm 1 grade) was ungraded even after we had taken the final. That is 7 weeks worth of waiting. By week 8-9, most students still didn't know what their grade would look like, but the pass/fail deadline was quickly approaching. Students had to decide between literally gambling with a passable letter grade or to just completely forsake the class grade. Besides taking a load of time to grade, the graders often made mistakes and would take off points for answers that were clearly correct. It was a common occurrence for students to receive 0 points as if they left an answer blank, when the (correct!) answer was clearly on the sheet. This would typically lead to a regrade, but Barr decided to institute the arbitrary rule that students would only be permitted 3 regrades, and if all of them were rejected, then you would lose that privilege for the entire quarter. And the regrades had to be worth a certain amount of points for them to be even considered. At best, the questions can be described as a "tossup" since they would ask concepts from mRNA vaccines to tire pressure to self-assembling microlayers.

I really hope Barr fixes his class as time goes on, because my quarter was a mess. For those of you thinking about taking Barr: run. Felker would arguably be better since at least he lectures on material and gives homework with problems actually reflective of the exams.

The class structure is the main thing that is annoying with this class. Barr himself is okay, the lectures are just okay. You should definitely read the textbook because the lectures alone will not be enough. Also, the tests are very difficult compared to some of the problems he gives you. However, the grading is sorta lenient while also being sorta confusing.

The class is essentially one OWL HW section per chapter, ungraded discussion worksheets, and the occasional group HW. There are two midterms and a final. The OWL HW is fine and easy. The ungraded discussion worksheets are participation based so that is also fine. The group HW can be annoying, but if you get a good group you should be fine. Luckily everyone in my group was in the US so we only had at most a 3 hour gap between us, but if you are international, scheduling meetups to do the HW is going to be annoying. Also for international students, there is only one exam time. You have to show up, regardless of time cause Barr didn't create a separate exam for a different time slot. You need to be on Zoom during the tests, because that's how you're supposed to ask questions about the test and it is where any updates will be given. The tests are very difficult. You'll cover a lot of chapters. Most of the time, we were doing the chapter's OWL section a week before it was actually covered in class.

The worst part was the structure, especially online. In the class there is an expectation that you meet up and work with other people since the weekly practice problem sets, one of the only study materials, has no answer keys. You need to go to office hours to get them, which is pretty annoying. Also, it was hard to find the motivation to either go to OH or set up meetings with classmates since it was online. Additionally, the whole Zoom meeting during the tests was pretty useless. On the first midterm, we got an extra 10 minutes but it was only announced in the chat, so plenty of people missed it.

So if you take this class, be prepared for a difficult course with a high workload if you want understanding of the content and difficult tests that have little plug and chug. Barr is okay enough, but the way that the course is designed isn't great. Especially if you dislike chemistry, be ready to not do that well. The class requires a lot of work, you can't skate by with just lectures and HW.

I have never been so worried about not passing a class till I took 20B with Barr. After having Felker I was so ready for a new professor who would actually teach me chem. Well, I quickly realized that wasn't the case. I would go to lectures feelings completely overwhelmed and lost (which was mostly because I suck at chem.) He kinda goes his own way with certain topics like entropy he says "I know most people say it is disorder but I don't like that so that's not what it means." Which was the easiest way to understand such a conceptual term. To understand any of what he was doing, I rewatched lectures over and over again and used youtube, chemlibre and a million other resources. Also, I tried going to OH but he calls on random students which stressed me out so much because I was usually clueless. The problem sets didn't have an answer key so they seemed pointless to do. OWL was also a waste of time. Also, he has us put into groups of three-four to do homework sets which were ONLY assigned during the weekend (6pm Friday to 10am Monday) and all my group members as well as me worked weekends so it was extremely difficult finding time to meet. The midterms were beasts. He also promised us we would have our grades back within a week and we didn't get the final midterm 1 grade back till 2 days before grades were due for the quarter. We never knew how well or bad we were doing because of this and there was no curve but everyone claims to have done wayyy better than anticipated. I ended up switching to P/NP after he told us we HAD to get at least a 50% on the final and judging on my midterm grades this seemed more daunting than it should have been. I know Barr meant well but at the end of the day just avoid him unless he fixes the many mistakes.

Once final grades were posted, my opinion on Barr changed a little. The whole quarter, he seemed to be almost ruling with an iron fist and grading quite stringently, but I think he curved the final grades. He kept telling us that there would be no curve, but I got an A, when it was almost mathematically impossible to get an A in the class unless I aced the final, and we are all unsure about our grades from the final exam because he might not give them to us. So, if he actually did a secret curve, this class wasn't too bad.
The class is broken down into OWL, Homework, Discussion, Midterms, and a Final. Basically, the OWL and Discussion is a free 20% of your grade, and most of the homework is free too, which is another 18%. The first midterm wasn't bad, but he had a trick question that messed me up, and he does not believe in grading with propagation of error, so since I read the initial problem wrong, I essentially lost all points for the problem, even though I did the rest of it correctly, which was a bit unfair. The second midterm was very hand-wavey and obscure, but I actually did better on it because the problems looked more difficult than they actually were, and he gave us one less question than the first midterm. He also gave us some very simple problems that seemed to be free points. Also, on all exams he gives 5 free extra credit points for writing the integrity statement and signing it. Last, the final was definitely easier than both midterms by a decent amount, but there were a lot of spots where you could make silly mistakes, and I definitely did. Still, in the end he seemed to have realized his mistakes and curved the final grade, which I greatly appreciate.
Also, every week he sends out an optional weekly problem set which are quite difficult, but he basically gives all of the answers in office hours. The only inconvenience is that this is basically the only way to get answers and attending 2-3 office hours every week is a hassle. Getting these answers is key, though, as he uses the exact same questions on the graded homework assignments, and the exam questions are also similar.
Overall, if there's another choice, I'd probably take them over Barr, but in the end, he wasn't too too bad. He's a little bit "too nice" if that makes sense, like borderline fake since he used to work at Disney, but he's very intelligent, helpful, and caring. So, he's really hit or miss based on how strong your chemistry background is. The class seems way harder at the time, but in hindsight, Barr's class was probably average for a general Chemistry class. The workload is very light.

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tbh his class is hard af but u sure do learn a lot… im a chem major and this class has been making me consider other majors :) if you don’t have a choice and end up taking Barr u seriously need to have an open schedule because office hours is the only time where you can ever get answers to anything and they’re basically extensions of the lectures cuz some of the info covered there is so important. Don’t take this class with a heavy schedule because it will take up the majority of your time. He refuses to curve and the final we just took was god awful. His exams are extremely difficult just like his problem sets are (except without the internet or ur notes) good luck lmfao and do the problem sets and go to office hours and prepare to sacrifice a lot

DISNEY ADULT!!! That right there should say enough but for real I haven't met a single person in this class who likes him. He won't give out answer keys to the practice problems (even the ungraded ones which makes no sense) so in order to get answers for anything which is crucial, you have to sit through hours worth of office hours each week, which is so inconvenient. In addition, he uses exams as an opportunity to try and trick students and test out new things that we have never learned that are so loosely related to the actual topic. Overall, do not take him if you do not absolutely have to.

Worst Professor ever! In this class you don't need to spend any time on review sessions cuz the exams are just unrelated to the lecture at all. This professor is trolling. Avoid him at all cost even though it seems Chem20B is only taught by this guy.

Do not take this class with Barr if you can avoid it. Unfortunately, he was the only 20B professor this quarter, meaning I was stuck with him. I thought that my knowledge from AP chem would be enough for me to get through this class rather easily, and up until the first midterm, his lectures reflected that belief. His lectures make the material seem pretty reasonable; however, his "optional" problem sets (that he doesn't provide answer keys for) and his exams display how surface level the topics covered in his lectures are. He covers the bare minimum during lectures, but then tests you on a much deeper and confusing level. His lectures are also very chaotic, start five to ten minutes late, and are extremely rushed.
The first midterm was pretty confusing, but it was nothing compared to the second midterm (class average was around 60). Barr's exam questions don't test you on your mastery of the topics; they test you on how well you can decipher his bullshit in order to figure out what he is actually saying. His questions are long-winded, convoluted, usually are on things never covered during class, and are only vaguely connected to class material.
Barr also likes to pride himself on having his students interact with him, the TAs, and other students. None of this interaction is voluntary. His homework assignments, two of which are due right before exams, are completed in groups assigned by the TAs, and are significantly easier than any test question, making them time-consuming busy-work. Barr "encourages" his students to do the problem sets and come to his office hours, but it is clear that these things are necessary in order to do well in his class.
In the beginning of the course, he says that he goes over problem sets in his office hours instead of providing answer keys. I only attended a few office hours, but during this time, he rarely completed a full problem set, leaving the other questions unanswered and was unwilling to provide the answers.
Ultimately, this class is too much work and purposely made more difficult by the exams. Barr seems like a really nice person, but is an unorganized and stress-inducing teacher.

Professor Barr is a very nice man. I would enjoy spending time and just talking to him. As a teacher? That's a different story. KEEP IN MIND this was his first quarter teaching ever so he will probably improve.

I feel like his expectations of us were unfair. He expected us to be chemists when quite a few of us were engineering students who will never need chemistry again. His tests were difficult but not impossible, but he did not prepare us for them. Before the first midterm we expected his tests to be relatively easy because he said they would be similar to the homework (which was easy) and boy were we wrong. On the second midterm I did much better just because I knew his testing style and could study and adapt for it. I think if you study hard you'll be okay.

Barr would also answer questions with "it depends" or "sometimes" and generally refused to give straight answers to any questions because "there is always a time where always doesn't hold" or something along those lines and it was incredibly frustrating, but if you ask the TAs and LAs they will give you a real answer.

Most of my complaints with Barr are things that I assume he will fix for his future classes and I'm sure you can read about them in the other reviews (slow grading, having to do multiple chapters per week, expectations that we could go to every office hour, not giving us the answers to the problem sets, etc). He was very engaging and cares a lot about his students, but everyone could tell that he was new and overwhelmed.

I think if you have to take Barr he will not be the worst, but if you have the option of a different professor with better ratings I would go that route.