I was in Prof. Li's Chem 20B in Summer 2015. This is the first time that Prof. Li taught as an instructor, after she got her PhD in UCLA physical chemistry in Spring 2015 and her UCLA Distinguished Teaching Award (TA) in Winter 2015. Simply put, Prof. Li is the best instructor I have so far at UCLA. (I am a Junior.)

Li is helpful and good

I had Professor Li for 20A and 20B, and got an A in both.

Her classes are about as easy as chemistry classes can get. If you're a major that doesn't "need" chemistry in terms of actual future coursework (or perhaps already know enough from a good AP chem class) then go ahead and take her and have a good time. Otherwise you might want to consider the other professors teaching. I only say this because, even though she is a gem of a person and a godsend as far as not having a terrible gen chem experience goes, her classes may leave you unprepared for other classes if it's your only exposure to gen chem material. This isn't because she doesn't teach well, as she makes every effort to do so (she actually rehearses her lectures beforehand around 10pm in the CS lecture halls). It's because the way she tests you on material doesn't really ask you to know much chemistry: you just have to be able to tell what equation on the equation sheet to use, and how to competently punch the numbers into your calculator.

However, I don't think it would be fair to review Professor Li without detailing how great of a person she is: she has plenty of office hours, and holds multiple review sessions (yes, she does them and not the TA's) which usually include pizza that she buys with her own paycheck. She also gives out "awards" (which I think are chocolates but am not really sure) for improvement in the class.

She really does want you to learn, so if you have enough motivation to do so, then take her class. If you don't then maybe you should still take her because a lot of the other gen chem professors are garbage.

Snacks during the five to six office hours held every week. Where can you go wrong? Li is an extremely kind professor, taking the time to get to know the names of hundreds of students, and hosted extensive office hours and review sessions with free food at each of them even when she didn't have to. She is a clear lecturer and is clearly well-educated and passionate on the subject matter. The workload was fair and manageable, and the problem sets gave good, thorough practice on the material. All the TAs were also extremely approachable and knowledgeable.

The bad part about this class is that, to compensate for the absolute grading system (98% = A+, 92 = A, etc.), the midterms and final are all extremely easy, which can give the impression of a lack of challenge. The midterms in particular were nearly carbon copies of the practice midterms she handed out, with perhaps one or two additional concepts tacked onto the end of a question. The final was more challenging, but was still quite straightforward. All of this made for a very easy A in the class, so much that I worried less about this class than about my GEs. However, despite the easiness, I felt like I did learn all the concepts covered very well. Overall, I would recommend taking this class, although you may be wary if you want a real challenge, since the focus of this class is moreso learning than trying to get a good grade and the A is pretty much given to you if you do the work.

But given your other alternatives for 20A and 20B, I'd still probably take Li in a heartbeat.

Professor Li is insanely nice and the class is pretty important to do well in because the material is very important for future classes. HOWEVER, Professor Li goes WAY too easy on her students. All of the midterms are almost direct copies of the practice tests which results in everyone getting high grades on them. She uses a "no competition amongst students" breakdown which is great but I don't think I really learned anything because of how easy her tests were. The only test that was actually different was the final which I'm sure came as a shock for many.

Take her if you want the easy A. I definitely appreciate the 4.0 but I didn't get much out of her class.

I had Professor Li for both Chem 20A in Fall 2015 and Chem 20B in Winter 2016 (I recieved a A+ in both). Professor Li is without a doubt the nicest and most caring professor at UCLA. She definitely goes above and beyond her call of duty as a professor by offering office hours 3 times a week, providing snacks at office hours and exams, and holding 3 hour long review sessions. At office hours and in lecture she tries to learn every students names and by the end of Winter quarter, she knew most of her students since many took her for both 20A and 20B. In both Chem 20A and Chem 20B, SHE GIVES ALL COURSE MATERIALS FOR FREE. She prints out 350 copies of every lecture note, homework packet, and practice self evaluation and hands them out in class to all of the students in order to "conserve cost for you".
To be honest though, she is a really easy professor and you should be ashamed if you get lower than an A- in the class. She gives you the practice midterms and finals before the tests, which are basically identical to the actual self evaluations (her name for exams). However, just because she is an easy teacher, does not mean that she is a bad teacher. I felt engaged throughout her lectures and I felt that I actually learned chemistry well despite the easiness. It was a breath of fresh air not having to worry about my grade and learn for the sake of learning.
I did feel that she was more enthusiastic about teaching 20A over 20B since her real passion lies in Quantum Chemistry, which is the topic of Chem 20A. 20B was more boring but she still did a good job.
All in all, I loved Professor Li and I would recommend her class to every student wanting to take General Chemistry at UCLA. 10/10.

She is really, really, really nice, probably the nicest professor I would ever have in UCLA. I had her in summer for 20A and winter for 20B, and received A+ for both classes because she was so easy.
She is good at explaining concepts and telling chemistry jokes. She would tell you the bottom line of each concept, and test you very very basic materials. She has tons of office hours and gave out snacks during office hours and review sessions. There is no possibility that you will not like her because she is such nice girl.
The only complain that I had about her would be similar to the post below. Her tests are so easy and basic that what she taught would probably not build up a solid foundation for 30 series chemistry because if you memorize all questions from her practice exams, you will do well in the actual exams. In the winter quarter, there are two holidays on Monday and she did not have time to cover everything she wanted. The whole chapter of "Acid and Base Equilibrium" was skipped, and these concepts were really important in 20L. In 20A, she also skipped something that is important to know.
Those were the first time she taught 20A and 20B, and I believe that if she become more experienced, she can become a really really fantastic professor.

If you want an easy A in 20B, take Li. I studied for maybe an hour for each of the three tests, often missed lecture, and still pulled an A+. While she is effective in teaching the basic, high-school level topics of this class, its simplicity stems from the fact that in no way does Li challenge her students to apply these concepts to complex problems. Her homework problems are the same as the textbook problems, which are the same as example problems in lecture, which again are the same as her exam problems.

Li seems like a genuinely good person and I'm sure she could be a great professor if she challenged her students. As is, however, this class offers 0 intellectual stimulation and I can only recommend it to those who would like to boost their GPA, yet are indifferent towards advancing their education.