Gatsby can see Daisy’s dock from his house, which was a primary attraction for him in purchasing it in the first place. The scene at the end of chapter 7 where Gatsby stands alone, looking at Daisy’s house, is just after Daisy has run Myrtle down, killing her instantaneously. This scene is both sad and ominous. Gatsby is concerned about Daisy and wants to watch her house until he can see her bedroom light go out, which will reassure him that she is home safely and trying to get some sleep. Gatsby acknowledges to Nick that Daisy was driving the car when it hit Myrtle, but he says that he will take the blame.
In chapter 5, Gatsby has cajoled Nick into inviting Daisy for tea. After tea, he invites Nick and Daisy up to his house to give them a tour. He wants to show Daisy how much he has in order to impress her. He wants her to know of the opulence of his house, his hydroplane, his clothing, and, in fact, all of his impressive material possessions, such as his “toilet set of pure dull gold.” They plan to go out to the water to look at the Sound, but it begins to rain. The three of them stand together looking at the Sound.
"If it wasn’t for the mist we could see your home across the bay," said Gatsby. "You always have a green light that burns all night at the end of your dock."
Daisy put her arm through his abruptly but he seemed absorbed in what he had just said.
The two scenes are very different. Gatsby can watch Daisy's dock and house, which keeps her near to him in his mind. He could imagine Daisy in her home and feel how close he was to her. In chapter 5, he watches her home, or the green light at the end of her dock, with Daisy and Nick. She is standing right next to him, watching her dock with him.
Nick says of Gatsby, “he was consumed with wonder at her presence. He had been full of the idea so long, dreamed it right through to the end, waited with his teeth set, so to speak, at an inconceivable pitch of intensity.” In chapter 5, Gatsby feels that he is on his way to achieving his goal of attaining Daisy. Conversely, in chapter 7, Gatsby's life is about to be turned upside down and ended, largely because of his obsession with Daisy.