What are some symbols and themes in chapters 7-9 of "The Great Gatsby"?So far I only have the puppy collar as a symbol.

One possible symbol, connected with the smoldering yet unrequited love between Gatsby and Daisy is the weather, which is unbearably hot. On the train to the Buchanans’ for lunch, Nick observes that the day is “the warmest day of the summer”. He describes it as “broiling.” Straw seats “hovered on the edge of combustion,” and the woman sitting next to him “lapsed despairingly into deep heat with a desolate cry.” The conductor complains about the heat, an observation Nick follows with the fragmented and sardonic commentary, “That any one should care in this heat whose flushed lips he kissed, whose head made damp the pajama pocket over his heart!” Thus the heat of the summer in the city and the heat of passion in Gatsby's relationship with Daisy are emphasized. The physical heat of the sweltering last day of summer is no more intense than the fiery emotions—temper, passion, jealousy—of the characters.

Another symbol is Gatsby's car. That Daisy openly prefers riding with Gatsby shocks and appalls Tom, but he acquiesces, insisting that they drive his coupé while he, together with Nick and Jordan, will drive Gatsby’s yellow open car with standard shift. When they stop for gas at George’s garage, Myrtle sees from the upper window and assumes that Jordan, riding with Tom, is his wife. Cynically, Tom allows George to think he can buy Gatsby’s car; he is, thus, led to believe that the car belongs to Tom. On the return trip, however, Daisy and Gatsby drive the big yellow car, “the ‘death car’ as the newspapers called it,” a fact that leads George ultimately to seek information from Tom about the owner/driver. Nick’s statement, “So we drove on toward death through the cooling twilight,” expresses not just the literal truth of the experience but the thematic point as well—the car, a symbol of the driving quality, the recklessness of these people. They could destroy the lives of others and then simply retreat into their money. The images of cars also reflect the restless nature of the characters. This driving nature appears in the repeated images of cars. To notice the kind of car the characters drive is to perceive his or her character. Gatsby drives one of “monstrous length” with “fenders spread like wings,” a “rich cream color,” the interior “a sort of green leather conservatory.” Recurring words, such as restless, brooding, and driving, reinforce the depiction of a restless American society in the 1920s.

Colors also come into play in these chapters. Yellow, and variations of it, play an especially meaningful role. New York City, symbolically through cream colors, comes a little closer to the golden world and lifestyle of the rich. This describes Daisy in particular. She was fresh with “many clothes,” the golden girl, the king’s daughter, “gleaming like silver, safe and proud above the hot struggles of the poor,” always remembered driving her white car. Gold and shades of gold—cream, caramel-colored, yellow—are dual in meaning. Clearly, they pertain to wealth and opulence, but they also associate with waste and decadence and cowardice. In this case, gold represents a sellout of America’s idealism and true character, at least as it was originally perceived.