Hii.....since you love science you can easily learn the exam portions and master them.
Now you have just entered class 11 so first read the theory part properly.When you are confident that you can answer all types of questions from theory part, move on to solve problems.
First clearly study worked examples.Understand them properly.Then move onto simple problems from exercise.If you couldnt solve some go back to worked examples and study again.Keep repeating this until you have solved all the simples problems from exercise.Once you have finished it go for the tougher ones.Remember that a single problem can be solved in many ways.So choose the best and shortest method.
Problem solving technique can be mastered only by practice.Now you have a lot of time to practice.So please dont give up preparing for IIT.
Once you get the problem solving technique then you will be among the best in your class.
ALL THE BEST..