Dear Ankith,

Mostly students found Maths and Physics tough as compare to chemistry.

It also varies as per the students. 

To crack your exam for IIT you need to do lot of practice.

You can take help of NCERT books to clear your concepts and to build your fundamentals strong. You can focus on the topics which carries more weightage in the exam. 

Refer previous year papers and mock test series for your practice and to analyse your preparation level at regular interval of time. 

All the Best!!