Scenes in modern popular movies last an average of two minutes. They can last from a few seconds to several minutes, if needed. Sometimes scenes just give information, like seeing a shot of a car speeding to get somewhere. But main scenes are like little stories. There is usually some conflict - conflict is the heart of drama.
Tension builds until one character changes directions or decides to change things.
Usually at least one character will change emotional states during the scene. He enters happy, leaves mad. She enters aloof, leaves touched. Shaun's sister, Elizabeth, passes him with her boyfriend, John, and coyly asks Shaun if he has a date for prom yet, making him feel bad. Geeks never get a date.