In the seventh chapter of To Kill a Mockingbird, Scout and Jem are dealing with the after effects of their nighttime expeditions to the Radley place. Jem had lost his pants on a fence and later gone back for them in spite of his fear

As the chapter opens, Scout is reflecting on Jem's moodiness. She decides to leave him be and notes,

As Atticus had once advised me to do, I tried to climb into Jem's skin and walk around in it.

She realizes that if she had gone to retrieve her pants from the Radley place in the middle of the night, she would be moody, too, at least. She actually dryly remarks that her funeral would probably have been the next afternoon. Scout is learning empathy, and this quotation also reveals how much she respects the guidance of her father.

One October day, the children are walking past the tree in the Radley yard. They have found small items in the tree's knot-hole before, and now they notice something again. Scout explains,

Jem let me do the honors: I pulled out two small images carved in soap. One was the figure of a boy, the other wore a crude dress.

Readers suspect that Boo Radley is leaving these little gifts for the children, reaching out to them in the only way he knows how to and can handle. These small items show his interest in Jem and Scout and demonstrate his care for them.

One day, the children actually find a broken pocket watch in the knot-hole. Jem wants to try to fix it. He has been carrying his grandfather's watch once a week, but as Scout notes,

On the days he carried the watch, Jem walked on eggs.

Jem has realized that having a prized possession involves responsibility as well as enjoyment. Carrying the expensive watch without breaking it or losing it has become a chore for Jem, a “burdensome task.”

By the end of the chapter, Boo Radley's brother has cemented up the knot-hole. He claims that the tree is dying, but when Jem asks Atticus about it, Atticus doesn't think that's the case. Jem is strangely quiet after he learns this. In fact, he stays out on the porch. “When we went in the house,” Scout says,

I saw he had been crying; his face was dirty in the right places, but I thought it odd that I had not heard him.

Jem is mourning a connection that he doesn't completely understand, and he is upset that an adult has been untruthful. Further, he is growing up. He no longer bawls like young child. His tears are now quiet, and perhaps he isn't completely certain why he's crying in the first place.

In Chapter 7 of To Kill a Mockingbird, there are several meaningful quotes. At the beginning of the chapter, Jem shares with Scout what happened the night he went back to retrieve his pants. Jem expected to find his pants exactly where he had left them—stuck to the barb wire fence. Instead, Jem found them crudely mended and neatly folded across the fence. Jem tells Scout how it made him feel:

"When I went back for my breeches—they were all in a tangle when I was gettin' out of 'em, I couldn't get 'em loose. When I went back—" Jem took a deep breath. "When I went back, they were folded across the fence. . . like they were expectin' me."

Jem tells his sister that he feels as if the person who did this knew him well. It puzzles him.

One day, Jem and Scout spot a ball of twine inside the knot-hole of an old tree on the Radley property. Jem tells Scout to leave it, as he believes someone is using the knot-hole as their hiding place. After several days, the twine is still there:

We went home. Next morning the twine was where we had left it. When it was still there on the third day, Jem pocketed it. From then on, we considered everything we found in the knot-hole our property.

This is the beginning of the children eagerly checking the knot-hole for gifts. They find many items in the knot-hole, including carved soap figures, an old spelling medal, and chewing gum.

Jem and Scout decide to write a letter to their mysterious gift-giver. They intend to place the letter inside the knot-hole. When they go to the tree to deliver it, they make a sad discovery: the knot-hole has been filled up with cement. They discover that Mr. Radley is the one who did it. They ask him about it, and he tells them he did it because the tree is dying. They ask Atticus about the tree, and they discover that Mr. Radley had been lying:

"Why no, son, I don't think so. Look at the leaves, they're all green and full, no brown patches anywhere—"

"It ain't even sick?"

"That tree's as healthy as you are, Jem. Why?"

"Mr. Nathan Radley said it was dyin'."

They know Mr. Radley does not want them to find anything else inside the knot-hole. This is why he lied to them.

These quotes show the meaningful parts of Chapter 7. Most of the chapter centers around the gifts found in the knot-hole, though Jem's story at the beginning is also important. All of these quotes are evidence that Boo Radley wants to befriend Scout and Jem. His mending of Jem's pants and his giving of gifts are signs of kindness and friendship.

This is a good question. There are many great quotes. Let me give you three of them with a few comments. 

First, we have the opening of the chapter. In this context, Scout is trying to see things from the perspective of another person. This is importantly, because it is a sign of maturity. By the end of the novel, Scout would have matured to the point of being able to do this. Chapter seven is her first attempt. 

Jem stayed moody and silent for a week. As Atticus had once advised me to do, I tried to climb into Jem’s skin and walk around in it...

Second, this is also the chapter when Scout and Jem find mysterious gifts in the tree knothole. These gifts will continue and increase the suspense of the novel. There is some suspicious that Boo is leaving these gifts.

Jem let me do the honors: I pulled out two small images carved in soap. One was the figure of a boy, the other wore a crude dress.

Finally, the other main action of the chapter is when Nathan Radley plugged up the knothole, so that there would be no more gifts. This is significant, because the budding relations with the mysterious person leaving gifts and the children is now gone. 

“Tree’s dying. You plug ‘em with cement when they’re sick. You ought to know that, Jem.”