He will fidget his body and not look you in the eye plus try to change the subject. If you asked him to do a disagreeable chore, ask him how he feels about doing it, and don't beat hell out of him when he gives you a straight answer. If you are thinking your son is having problems at school or other problems not related to home he's act moody, could be depressed, fiddles with his food, is quiet, but could snap at you. Try sitting down with him and communicating. Tell him you were young once and had all sorts of problems and he can trust you. If he won't open up and it gets worse then I would seek counseling as he is more likely to open up to a psychologist.