You may be enrolled in a science course and your instructor may have suggested you look at this site. Or perhaps a friend recommended it, or you discovered it on your own. While ie-chemistry and ie-Physics are assembled a bit like a traditional sequential study of chemistry and physics, you may pick and choose what you want to access and study.
If you are following your instructor's suggestion, it is likely that your instructor will be willing to grant some credit for your efforts if you are willing to document what you read, what experiments you try, and write a suitable report about what you accomplish.
If you arrived here without knowledge of your instructor, may I boldly suggest you also try to keep a record of what you read and what experiments you try. Having known many very good science teachers, I hazard a guess that if you can explain what you found and what you managed to accomplish, there are reasonable chances you might negotiate some credit for what you've learned. Go for it!
Finally, compared to the first classroom, the introduction of the first printed textbook, or the introduction of a teaching laboratory, web based instruction is very new. While I've done my share of classroom teaching (40 years), I'm a novice at web teaching. Everyone is. So please consider all you find here to be early β quality. You might find much that needs improvement. That is less likely in the science, but clearly science hasn't reached perfection yet either. But most likely you will find instruction that is awkward, unclear, or misleading. Improving web based instruction will take people like you to spot the problems, and hopefully sometimes even suggest how it might be made better. You'll find my name at the foot of every investigation. If you click on it, it should initiate an e-mail where you can send me your thoughts and suggestions. I very much appreciate all the help I can get improving this project.
I wish you the best of success in your efforts.