Jem was obviously disturbed by the fact that Mr. Radley had filled the knot hole with cement. Why was Jem more upset than Scout?I've been puzzled...

Jem is growing up and is beginning to understand more about the world in which he lives. He shows no fear when he asks Mr. Radley why he cemented the knothole in the tree, and he doesn't accept Mr. Radley's answer. Jem can see through Mr. Radley's lie. He is letting loose of his childish fears and superstitions about Boo Radley. He begins to put two and two together, remembering how his pants were mended when he went back to get them. Jem also isn't afraid to show his feelings about the knothole, which is another sign of his maturation. Jem understands the complexity of the situation, but Scout only knows that they won't be getting any more gifts in the tree.