Chapter 7 - "The Sorting Hat" - In which Professor McGonagall tells the first-years a bit about the school and they are sorted into houses by the Sorting Hat. Then Dumbledore welcomes them, they have a feast and find their dormitory for their first night at Hogwarts.
Harry's First Journey on the Hogwarts Express
Harry and Ron are visited by Neville, who is looking for his toad, and Hermione. They watch Ron try to turn Scabbers yellow, Hermione tells Harry about all of the books he's in, and she and Neville walk off.
The Sorting and the Welcome Feast