Professor Weiss is the smartest man I've ever met! He made this class very interesting and helpful for future purposes.
IMPORTANT NOTICE: This class is extremely challenging. If you do not have the time to fully invest daily hours of work for this class, do not take it. This class' workload is 3 times more than the regular Chem 20B class. There are creative problems to do each week, literature assignments, and also homework from the book. On top of that, there is a final project (poster + paper) that must be completed and is worth 15% of your grade. The only way to achieve your best is to try very hard on the homework (worth 30% of the grade), and to try and score above average on the tests.
Also, stay in contact with the TA's because at times their information is very confusing and the guidelines are difficult to understand. My experience with the TA's was rather disappointing because of their harsh grading and lack of communication, so please make sure that you precisely understand want they want. You can always ask Paul for help if you feel lost.

Warning: this class is A LOT of work. Weekly homework, literature assignments, and readings. Add that onto a final project, poster, and essay. Oh and midterms and finals, of course.
However, the class itself isn't that bad, and I don't regret taking it. Paul really does want all of his students to do well, and he'll help you get into a research group if you're set on one already. The TA's are also pretty cool, although their discussion worksheets do not help at all with the midterms and finals. If you enjoy learning chemistry for the sake of chemistry (like me), you'll like the class.
The bottom line is, if you're willing to put in the work and effort, you'll do fine in the class. It's whether or not you're willing to do all that work (as in, I took 4 classes that quarter and 20BH was half of my homework/studying time)

Weiss is definitely the best professor I've had at UCLA. Brilliant guy and very helpful. The only office hours I've ever attended were his and it was more for discussion and stories than help in the class. He is very well connected and willing to help you with anything inside or outside of his class. He hooks everyone up with lab positions and will talk to other professors about you to get you a position. I still see him around and say hello and talk a bit. What a guy.

Paul was a wonderful and approachable professor. The class itself was tedious (so much homework! There's weekly homework problems, a poster presentation and paper, creative questions, and literature assignments), but the exams were reasonable as long as you study. Much of the class (besides a few concepts) was a review of AP Chemistry, so the concepts weren't too difficult, but Paul definitely makes interesting test questions that requires you to apply these concepts to new scenarios.

Of course it's a lot of work, but it's satisfying work if you do it. Really great class for prospective any prospective chemistry-related majors. Weiss also cares a lot about your learning and is really nice guy. You won't regret doing this class.

Pretty shocked at how low his 20B reviews are. He's probably my favorite professor. Maybe if you're a tryhard, he's the kind of professor for you. He places a lot of emphasis on putting work into getting good grades - it's really hard not to do well if you try.

***I took this class in an online format during the COVID-19 pandemic. TL;DR at end.
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This class is a lot of work, but ultimately, it's an experience that's worth it. If you're deciding between this class and CHEM 20B, I believe you will have a better time in this class, as long as you're willing to put in a bit of extra work. It will save a lot of stress and worrying about poorly written exams or such.
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The homework in this class consisted of weekly problem sets, assigned from the textbook (which you can find online for free). These would usually be somewhat related to the lectures in class, but in general, seemed supplementary rather than complementary. Another weekly assignment was to design your own problem about a topic from the week, which is pretty simple. There's also the "Literature Assignments" — you choose a research paper on a given topic, and write a short summary. It's pretty time consuming, but it's a useful skill, and the grading on all three types of assignments is very forgiving. Your lowest score for each is also dropped. There's a large project in this class, where you choose some topic related to the class and heavily research it and make a poster and presentation. It is a significant amount of work, but it's also not difficult to do, and you get to choose your topic, so it's interesting.
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Lectures and discussions weren't exceptional, but they're certainly useful. Paul is a great guy, very nice during lectures and office hours. He's pretty easy to listen to and understand, and never makes it hard to ask questions. The class is also much smaller than other similar courses, so if you're somewhat active in participation, he'll know you personally. Participation was technically part of the grading, but I think that just meant "show up to classes and talk at least once throughout the quarter," so free points, really.
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The midterms were very fair, and also were 50/50 individual/group performance. After the individual section, you were allowed to consult with the whole class, and basically get a free 100 for the group section. Each midterm had a pretty significant amount of extra credit too. The final exam is an oral exam you have to schedule with Paul individually, but the questions are basically the same, he just asks you them in a call. That may sound bad, but you can just ask him for hints if needed, and he's super generous on the grading. If anything, the final is one of the easiest parts of the class. It was super nice to not be stressed about the final when I heard CHEM 20B students freaking out about theirs.
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Finally, there's tons of extra credit opportunities. There's an extra auxiliary lecture you can attend and do an assignment on for I think 2% of your grade, and the midterm extra credits were pretty significant too. I think most people reading this are just considering this or CHEM 20B, so here's the comparison: CHEM 20BH is more work and requires more self-interest/initiative, but is much less stressful and more inclusive since the class is smaller.
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Point distribution (there is no curve on exams or the whole class):
Midterm 1 - 10%
Midterm 2 - 10%
Final - 20%
Project (5% poster, 5% presentation, 10% paper) - 20%
Homework (10% creative problems, 10% textbook problems) - 20%
Literature Assignments - 10%
Auxiliary Lecture (each after the first is extra credit) - 5%
Participation - 5%
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Basically, only 30% of the class is individual exam performance (b/c of the group phases of the midterms). It's not too difficult to get an A since there's so many other assignments.
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TL;DR: If you're confident in chemistry (taken AP chemistry or a similar level class) or are willing to spend some time reading the textbook each week, just take this class. It's a much better experience than CHEM 20B, plus you can save it for second enrollment since it doesn't fill. If you're still not convinced, go read the 20B reviews for Barr, who was the option for Winter 2021. Or even 20B for Weiss, the same professor.

Although almost every review has already stated this, this class is an extreme amount of work and isn't something to be taken lightly. When I originally heard of the amount of work in this class, I thought that I would be fine and wouldn't need to worry about it. However, this class will be a lot of work no matter what despite what the grade distribution might show. There's a lot of homework and classwork to be done in this class and there was more work than my other three classes combined. However, the way this class is structured makes it so as long as you put forth your best effort and a little more, you won't have to worry about your grade which is nice. Midterms and finals aren't worth a large portion of your grade and are forgiving due to the group phase. Also, midterms and finals are online and open internet/note but there's a reason why it is that way. The midterms and finals are extremely difficult and you need to do research to work through them a lot of the time so good luck. In my opinion it does help you as a researcher since it forces you to think critically and uses your resources. It's worth noting that this class overall is more like a research class since the professor really wants everyone to be in a lab after taking the class and he will help you. Because of this, you can see that in the homework assigned and the way the tests are structured. For homework, other than the textbook problems, there are scientific paper review assignments and a final project where you do research which is why this class feels more like a research than a general chemistry class. Although I highly struggled in this class, I managed to end with an A and do not regret taking this class at all.

The workload for this class is A LOT, but Paul and the TA Katie are extremely generous with the grading. Most of your grade isn't dependent on the tests so you can get the lowest score on the midterms and still scrape through with an A like I did.

The class itself is really research-based/heavy, and you become really research literate by the time the 10 weeks are up. Going to Paul's office hours are a must if you want to join a research lab, as he will give out recommendations left and right for the students who took his class.

Chem 20BH is a significant amount of work; on top of doing the weekly textbook assignments, there are also scientific literature assignments every other week and a LARGE research project that creeps a lot faster than you'd expect. That said, I feel like I learned a lot and Paul and the TA/LAs are all very very helpful and all want to help you succeed. Office hours are a huge help (attending at least one is mandatory for participation), and a great way to get into research. If you're aiming to get connected with professors, this class is definitely worth it because Paul will go out of his way to help you out with that. The grading scale is weighted less towards the tests, but there is a lot of extra credit available so as long as you do all the work, your grade should be very favorable.