CHE 002A is probably one of the most notorious STEM classes at UC Davis. It is so notorious that getting a 50-60% on a midterm is considered "average". That being said, let me assure you - the class truly is not as awful as its reputation makes it out to be, dependent on the sort of student you are. Here are my complete thoughts on just about everything that comes to mind about the class as someone who did quite well in it during his first year.
First of all, let me break down the content structure of the class. You will be learning 7 chapters - Atoms/Molecules/Ions, Stoichiometry, Solution Stoichiometry, Gases, Equilibrium, Acids and Bases, and Applications of Aqueous Equilibria.
Atoms/Molecules/Ions
The very beginning - you'll learn exactly what makes chemistry, chemistry. Not explicitly why it's the study of properties of matter, but you'll learn the foundational material of things you'll be solving tens of hundreds of thousands of problems of. Atoms, molecules, and ions, as well as a general oerview of the periodic table and few properties (but not trends - this is for future sections in the series). It is absolutely imperative you do not fall behind here - being slightly uninterested in this section may cost you more than in any other. Straightforward enough, but a lot to absorb for a first chapter.
Stoichiometry
Admittedly, this is arguably one of the most brutal chapters of the series - not because stoichiometry is an extremely difficult topic to learn, but just because the expectation is that the complex logic and understanding of moles gets turned into a rather simpler equation. You will also be bombarded with a lot of conversions and units. You may have a decent chance of walking out of the lecture hall asking yourself how stoichiometry is a thing - but it is quite crucial in general chemistry at the very least. If you ever need a simple memory tool - just cancel the units. The execution isn't terrible, but the teaching system is awful for anyone because the time isn't enough.
Solution Stoichiometry
Redox (reduction + oxidation) is no joke. You need to apply what you learned about ions and electron transfer to determine how equations can be balanced. Oh, and I forgot to mention - if you aren't good with looking at equations, this chapter will force you to. You'll also learn about solutions for the first time - which will be extremely imperative for the last two chapters in the class. Please let molarity stick to your head the moment you learn it. I personally didn't think the chapter was that bad, but some of the long answer problems can be extremely time consuming and easy to make mistakes if not careful. Conceptually not terrible, but the execution can be very extraneous.
Gases
Conceptually quite tricky for me. You will learn a lot of fascinating applications, and this perhaps may be one of the most enriching chapters of the class, but nonetheless it is definitely one of those chapters where genuine understanding will benefit you. Please do not rely on memorizing ideal gas law, because this is where the chemistry gods can easily bite you if you don't truly immerse yourself on what each variable means. Pressure, temperature, and volume will be immensely important for equilibrium and certain chapters in 2B especially. I personally found MCQs from here to be the most punishing.
Equilibrium
Similar to stoichiometry, the concepts are simply not explained well enough on a scale for genuine understanding - you are simply expected to accept that equilibrium is a state where the forward and reverse reaction rates are "equal". This is a chapter where absorbing information is really crucial, because whilst the concepts aren't impossible to digest (and it's actually quite satisfying when you do), it is definitely a very tricky section if you cannot fully understand it. Equilibrium is also incredibly imperative for the final two chapters of this class, which are... on another level.
Acids and Bases + Applications of Aqueous Equilibria
The two most demonic chapters of the class by far. This is where my high school chemistry pedigree completely collapsed and I had to relearn everything from scratch. You'll be thrown the fact that an acid and a base is composed of H+ or OH- to a cation or an anion, and how they interact with water, the universal solvent. ICE tables from chapter 6 develop steroids and certainly become extremely complicated mathematical procedures. Chapter 8 takes it to the next level by introducing buffers and titrations - which lead to some of the hardest and most time consuming exam questions in the whole series. Your mathematical and algebraic fluency will be genuinely tested here. There is a reason most professors spend extra time in this region (especially for Aqueous Equilibria) whilst sometimes skimming over gases and equilibrium. I would honestly give the latter a shout for the hardest chapter in the whole 2 series. Aqueos equilibria, to put it simply, is if solutions, equilibrium, algebra, and acids and bases decided to have a baby. A very, very demonic baby.
Bottom line on the content - it starts off throwing a lot at you at once, and you may find yourself in a better place come the period of the first midterm. The storm will cool, and then you'll find yourself thrown back into the deadly waters when the final comes. Aqueous equilibria is only tested on the final exam, so the last period of the class will be extremely strenous. You are expected to find a lot of things intuitive whilst also having an adequate understanding of the topics - significantly disproportionately to a class like BIO 001.
The labs are no joke. You'll start off with basic chemical reactions, and then over a half of the class is basically titrations and aqueous equilibria. Chemistry labs tend to be extremely tenuous, but it is especially so in 2A - you will never have a guaranteed chance of not staying the full three hours. Please take them as seriously as you can. The chemistry department also has extremely high expectations of each and every student during the lab period - breaking the tiniest rule can be quite unforgiving.
Homework and discussion depends entirely on your professor and TA. Some of them will let you submit everything on the last week, whilst some will give you weekly assignments. Excluding Dr. Enderle, I believe every professor uses OWL, a solid enough system to get some practice in. The problems are very useful when studying for exams. As for discussion, I believe it is almost entirely mandatory, though the intensity of each session purely depends on your TA, given some will just let you do free work whilst others will make it an extra lecture of the week. Regardless, treat it like a class.
OVERALL - I find it a very viable class regardless of your professor. You will need to spend a significant time outside studying, and I'd say it requires more effort than any BIO or MAT classes for the typical student. For pre-meds especially, this will be a critical baseline of all the organic and biochemistry classes you will need to take for medical school, so please allow yourself to enjoy the material that comes to you. Though students with a stronger algebraic baseline may be rewarded the most, anyone can succeed if they put their hearts towards the class.
For freshmen specifically - *please take this in the fall quarter*. Taking the full series before your second year will keep you on track for many upper division classes and MCAT trajectory if that's what you're looking at. There are also some trends that show the fall is when the "better" professor options are available. Dr. Enderle, Gulacar, and Hayashi are all wonderful - and you can hardly go wrong with any of them.
Anyways, that was a lot. Do provide questions or comments if you have any - and let me know which class I should cover next.