If chemistry is your most difficult subject, then always study it before all other subjects. You must study chemistry when you are most alert and fresh. Make sure to take 5 or 10 minute breaks every 2040 minutes in order to clear your mind.
The first step is to determine exactly how long you have to learn chemistry. You'll need a lot more discipline to learn chemistry in a day compared with a week or a month. Also, keep in mind you won't have great retention if you cram chemistry in a day or a week. Ideally, you want a month or longer to master any course. But for the JAMB UTME exam, you can still do some cramming. Although we do not advice it.
1.) Brush up on your math.
2.) Memorize the periodic table.
3.) Study all the core concepts and learn how to solve problems step by step.
4.) Make flashcards.
5.) Learn mnemonic memorization techniques.
6.) Think three dimensionally.