What's the main difference between the SAT Subject Test for Chemistry and the AP Chemistry exam? Is one easier than the other, or are they comparable?
The AP Chemistry Exam is longer and more difficult than the Chemistry SAT Subject Test.
85 multiple choice questions
60 minutes total
Scored from 200-800
60 multiple choice questions
Seven free response questions (four short and three long)
3 hours and 15 minutes total
Scored from 1-5
The most obvious difference in format is that the AP Chemistry exam has free-response questions in addition to multiple-choice. However, there are also major differences in the way the multiple-choice questions are structured on teach test. For AP Chemistry all the multiple choice questions will ask you to provide answers based on data tables, sample reactions, and other experimental scenarios. It's all about applying your knowledge of chemistry to new scenarios.
The SAT II, on the other hand, has questions that will ask you to demonstrate basic factual recall. For example, you might have to identify which ion out of a given set of choices is found in a particular chemical compound. There are also "relationship analysis" questions, which prompt you to choose whether different statements about chemical properties are accurate (there are special true-false answer grids for these).
The main difference from a content perspective is that the AP Chemistry test consists entirely of questions that ask you to apply your knowledge of chemistry, whereas the Chemistry SAT II includes many questions that just ask you to restate it. AP Chemistry takes things to a more advanced level.
One thing I would like to point out, though, is that it's objectively easier to get a 5 on the AP test than it is to get an 800 on the Subject Test. You can get a fair amount of questions wrong on AP Chemistry (around 30 percent) and still earn a 5. You have to get nearly every question right to earn an 800 on the Chemistry SAT II. Still, because the material on the AP test is harder, it will require more preparation if you hope to do well.