In English you sometimes pronounce words in very different pitches/tones to express your emotions. For example when you're offended, surprised or when being sarcastic.
Depending on the situation you may for instance answer a question with a sort of falling tone "No.". If the question offends you may answer "No." with a sort of falling-rising tone, almost as if it's a question. Or if you are uncertain if the anwser should be yes or no, you may answer "No." with a kind of rising tone as if you're asking a question.
Now I wonder how this is done in Mandarin because if you just change the tones of the words, you might actually change the meaning.