If you study hard I am sure you will do great
But if you do not get at least 6s in your sciences, I would not apply for them as you will have difficulty catching up with the content. The subjects are not easy but they are fun, so if you put your effort in, I am sure you will do great.
(I hate physics so I am cheering that you change to maths but it is all on you)
Remember that you are choosing the 3 most content-heavy subjects that require at least 7 hours+ outside of college time to revise, revise and revise.
FOr someone who just started college this year, I can tell you that I am still trying to cope with the amount of knowledge I have learnt, whilst I got decent grades of 8s and 9s.
All I can suggest is to revise exam questions