In Chapter 15 of To Kill a Mockingbird, what does Scout's childish attempt at a conversation accomplish?
In this chapter of the novel, there are a couple of instances of strange behavior from Atticus, which make the children suspect (correctly) that something is wrong. Near the beginning of the chapter, a group of men arrive on the Finches' doorstep, and Scout overhears an altercation about Tom Robinson. Later in the chapter, Atticus, carrying a light bulb and an extension cord, tells the children he's going out and proceeds to drive his car to the jail. Scout and Jem follow to find him reading outside the jail by the light of his lightbulb. As the children watch, a group of men arrive and begin to issue threats. At this juncture, Scout, afraid for her father, runs out to protect Atticus, who is rightly afraid; he tells Jem to take her, along with Dill, back home. When Jem protests this, he's grabbed by one of the threatening gang, who Scout then kicks.
It's at this juncture that things seem very tense and as if they could go horribly wrong, but Scout then does something unexpected—she begins to address Mr. Cunningham, the only person in the crowd she recognizes. The very power of her childish prattling is in the normality of it—she asks him ordinary questions about Walter and about his entailment. While he does not answer for some time, eventually he gives in, tells her he will say hi to Walter for her, and tells the others that it's time to leave. Scout doesn't understand how she has caused the violence to dissipate, but effectively, she has shamed Mr. Cunningham into leaving. Her childish innocence makes Tom's murder impossible. He is unable to continue behaving this way in front of a girl who clearly believes him to be an upstanding and ordinary adult. As a result, the altercation is, for the moment, averted.
Scout's attempt at a conversation dissipated a potentially violent altercation between the strange men who were talking to Atticus at the jail where Tom Robinson was held. Apparently Atticus suspected of a mob would show up to harras, lynch, burn, or attack the jail where Tom was being held.
Hence, Atticus goes to the jail to make sure nothing happens. His hunch is right; these men show up and had start making trouble. The interruption of Jem, Dill, and Scout may have been the very welcome interruption that Atticus needed to calm down the fiery characters, and to dissipate the action that was about to take place. The look of surprise on Atticus' face confirms this; Scout and Jem save the day.
This ended up stopping what could have been a horrific disaster. People were there in order for Tom Robinson to get hurt but when Scout sees all the men and confronts them, the reason why this is so important is because when she singles out Walter, he is able to think about what he is doing and how that is wrong, and because of that does not go through with the mob mentality esp since Scout is there.
Scout's childish attempt at the conversation with Mr. Cunningham stopped a what could have been a violent meeting between the men that met infront of the jailwhere Tom Robinson was held, because in talking to Mr. Cunningham (Walter's dad) and telling him to tell Walter that she said,"Hey." In turn Mr. Cunningham feels guilty, and he suggests that the men should leave.