I took Scerri for 20B last year, and I believe he is a very effective professor. The course is based off of the reader, so as long as you have a solid grasp of the content in the reader and the practice problems, you should be set. The exams if I recall are mostly calculations and problem solving moreso than conceptual (although he had some proofs on exams for various gas laws).
The positives I would say is that he presents all the material you need to know to succeed. The exams are almost identical to the practice problems. He's had plenty of experience teaching g-chem to underclassmen, so he knows what he's doing. He also doesn't use Oxtoby that much (which is a real plus, because I personally think that Oxtoby is one of the most difficuly textbooks to learn chem out of if you don't have any chem experience)
One negative I would point out is that the class is very competitive. I think the average for the midterm was mid 40's out of a possible 53, and everyone gets 100% on the thinkwells. So you gotta be on top of your game and get every point you can possibly get.
Overall, good professor and interesting class. I didn't take AP chem, and just studied the material everyday for about 45 minutes and ended up with an A+
And compared to Neuhauser who I had for 20A, Scerri is the way to go.

I took 20A and 20B with Scerri and I hated every minute of it. I loved Chemistry in high school and still liked the material but he made it terrible. He may be a decent lecturer but is job is to be a teacher too and he is terrible at that. He constantly makes fun of anyone who asks a question in class which I found to be totally inappropriate. He podcasts his lectures which is nice because that way you can make use of the mandatory $75 hadwritten coursereader (typos included for free) and not go to lecture and just listen to the podcasts while looking at the coarse reader. It's exactly the same except that you cant ask questions which you wouldnt want to do anyways because he would just make fun of you and then not answer the question. I took 20B with him because I couldnt take it with another teacher because of scheduling issues but I wish I did not have him twice. Also his tests have rediculous questions on them that lend themselves to causing the students who studied to get them wrong and the ones who did not to get them right due to wording which is just stupid.

Really not a great lecturer. While he does go over the material in a timely fashion, he is clearly woefully unprepared when he comes to class. Sometimes he encounters material he is not familiar with and spends a good three minutes deciding if it works or not. He is also very sarcastic and has a superiority complex which makes him unapproachable and kind of a jerk. Obviously is not in the field to teach students. He charges an absurd amount of money for the course reader and makes you pay even more to take thinkwell quizzes.

Regarding his exams, the first one for my class was very easy, and reasonably well written. His final though was literally the worst experience in my life. It was nine very difficult questions, two or three of which were completely removed because he conveniently realized that they were written incorrectly and unsolvable. To make things even more annoying almost every exam question was missing a key piece of information. Even the TA's were annoyed at how unprofessional and ridiculous the final was.

In conclusion, concern for student learning was below zero. I can't believe this guy is allowed to teach at UCLA. Only take him if you absolutely must.

If you take Scerri's class, you need to know one important thing: memorize the course reader! Everything he tests on comes directly out of his course reader. He also makes you buy this book of past exam papers; doing those before tests helps you study a lot too. Instead of homework out of the Oxtoby book (which you do not need to buy or ever look at; even Scerri's optional homework out of Oxtoby is pointless), you have to do Thinkwell quizzes. They are kind of helpful, but again, none of the tests questions will look like them. A part of me suspects that Scerri doesn't really have a whole lot to do with the creation of the Thinkwell quizzes anyway. Scerri's also a really entertaining professor and easier than other chem professors at UCLA, so take him if you get the chance.

Do not take this professor, if you are taking the early chem classes look for Felker or someone else... his class never discusses formulas or equations, and often times he answers a question by his own "intuition" which means complete guess... its a lot of self studying, memorizing the course reader, and banking on other students doing as bad as you.

There is only one rule you must hold true if you are taking Scerri: MEMORIZE HIS COURSE READER! If you fail to do this you are gonna have a harder time than normal. There really is no hard part to his class. Just memorize. And when i mean memorize, i really mean it. I underestimated that and as a result, when i took the midterm--i got owned (not that badly but u get the idea). Just memorize and you should be fine. He is a good teacher and in principle he really isn't that hard.

Scerri is an awesome professor. He's not as difficult as people say and he is definitely very entertaining. He will sometimes make fun of students but it's all in good fun. He does demos in class and gives you a 2 minute break during lecture. It doesn't sound like much, but it really does refresh you for the second half of the lecture.

His exams are not difficult at all. Everything on the exams can be found in the reader and you'll breeze through the tests if you go to lecture.

I would recommend this professor, especially over Baugh.

This class is easier than 20A. He's really pretty fair. Lectures are always worth attending, he's a pretty funny guy.

Two overhead projectors going at the same time... Dr. Scerri's trademark. I thought his lectures were very helpful in supplementing (or even replacing) the textbook. He does make fun of you if you fall asleep or ask a dumb question, so beware if you tend to do this. He really likes conceptual questions on his exams, but everything comes from the notes, so there are no surprises. Recommend highly.