YOU SAID:

I don't know, what is this for. How to chemistry?

INTO JAPANESE

これは何のためなのか分かりません。化学する方法は？

BACK INTO ENGLISH

I don't know what this is for. How to do chemistry?

INTO JAPANESE

これが何のためなのかわかりません。化学を行う方法は？

BACK INTO ENGLISH

I don't know what this is for. How to do chemistry?