Is this normal for a nine year old boy?

My son is the only child and he is nine years old. We spend time with him and love him with all our heart. Lately I've noticed he seems to be testing me and my husband by back talking. If we ask him to do something he puts it off until he wants to get it done or until we consistantly stay on him. He has been back talking for the past 2 months really bad and I'm wondering if he is just trying to run us over or is this normal phase he is going through. Please provide me with some extra parenting skills from parents ONLY!! We do things with him for example he we took him to busch gardens yesterday for Easter/Spring break trip and he still acts unappreciated.