Physical Chemistry is a specialized course, which is partial to physics and advanced mathematics. If you add physics as your subject, then I think you have an advantage in this respect. This course is difficult to learn. You'd better find a book on advanced mathematics in the summer vacation, because you have to learn it anyway. There are also a lot of materials and even teaching videos on the Internet, which are easy to find and learn well, which is very helpful for your future chemistry study (especially if you are majoring in applied chemistry and have a lot of calculations that require advanced mathematics)!
If you have more time, take a look at English, because there should be an English class within one month after you enter school, and fast classes and slow classes will affect your time for taking the CET-4 and CET-6. Believe me, English is very important!
As for chemistry itself, I don't think it is necessary to do it so early, because different schools learn different materials. If you can find information about your college education, you can still read it. If you look at other materials casually, it is not good for your study. As for high school knowledge, you should learn to let go. College and high school are still different.
I hope the answer is useful to you! I wish you a happy college life!