Personally, yes, I do believe that Hamlet is a changed man in Act 5. Before he leaves, Hamlet is full of grief and anger, the main source of these traumatic emotions being the man his mother married after his father's death - Claudius. Hamlet despises Claudius, because he saw his father as a "God-, and in his eyes no-one could replace him. This, in a way, dismisses Froid's Oedipal theory, believing that Hamlet had wanted to kill his father because he felt passionately about his mother.
The Closet Scene' falls in Act 3, Scene 4. In this scene, Hamlet is out of control. He has lost all common sense and makes wild accusations towards Gertrude, his mother. Hamlet has almost gone insane. After all, he stabs Polonius, who is behind the arras, thinking that it is Claudius, even though he has just seen Claudius at prayer. His sense of outrage at how Claudius has just invaded his life has made him furious enough to kill. During this scene, we get a sense of how important the mother-son relationship is. It is very intense and the power of it is seen in the language the characters use. Hamlet has dedicated more of his time and energy to the salvation of his mother, rather than taking revenge on Claudius. By using his crazy new attitude and anger, he is trying to convince her that she should not go to Claudius. This, however, is illogical, and will never work anyway because he will never be able to let go of the image of the King and his mother. Their relationship disgusts him, and he makes it clear in the language he uses. "And let him, for a pair of reechy kisses, or paddling in your neck with his damned fingers- (page 181, line 185). The mere thought of her sinning and going to Claudius' bed also disgusts him. For example, "And sets a blister there- (page 171, line 45), Hamlet is now referring to prostitutes. In this scene, you have to ask yourself - how much does Hamlet think his mother knows? He is bombarding her with accusations and information and she seems completely oblivious to all he is saying.
