How to distinguish between "ch" and "q" in Pinyin?

I thought maybe what you said should be pronunciation. because they have been distinguished in pinyin. only different writing. as for pronunciation, ch in Chinese is similar to tʃ in English. "q" in Chinese seems not to correspond pronunciation in English. luckily, I found two examples in English. as follow: q(i) →"chee" as in cheap ch(i)→"chir" as in chirp and you need to practise more. good luck!