how is jem changing? give several specific ways.

This really isn't a Chapter Four question. During the course of Chapter Four, Jem is still fully engaged in youthful play and pranks. It isn't until Chapter Five that Jem decides to exclude Scout based upon the fact she is a girl. Chapter Five also finds Jem in trouble with the neighbors and skirting trouble with Atticus. That's when the maturity begins to kick in.