In Chapter 5 of Rick Riordan's The Lightning Thief, what challenges does Percy face?
By the end of Chapter 4 of Rick Riordan's The Lightning Thief, first book of the "Percy Jackson and the Olympians" series, Percy has just successfully battled the Minotaur. Though his mother has disappeared in a flash of light, Percy has also successfully rescued Grover by dragging him into the woods to hide. In Chapter 5, Percy wakes up after having battled the Minotaur and doesn't know where he is. He is soon told that he is at Camp Half-Blood; that the Greek gods of mythology truly exist; that he himself is a demigod, or half-blood; and that he has to remain at Camp Half-Blood or else face more monsters. All of these revelations plus his new surroundings present Percy with plenty of new challenges.
One of his challenges is accepting Greek mythology as true. After hearing Annabeth talk about recently visiting the gods on Mount Olympus by riding the special elevator of the Empire State Building to the 600th floor and describing the quarrel between the gods she had witnessed, Percy feels very overwhelmed. As he explains to Luke back in Cabin 11, "I don't belong here ... I don't even believe in gods."
A second challenge he must face is bullies, just like the bullies he has had to face at all of his new school. This time the bully is named Clarisse, and she's the daughter of Ares, the god of war. As a prank, Clarisse drags Percy into the girls' bathroom. But when she does, Percy feels "a tug in the pit of [his] stomach," and as he has this feeling, water shoots out of the toilets and showers, combating Clarisse and her friends with water, driving them out of the bathroom.
In "I Play Pinochle With a Horse," Percy Jackson faces adapting to Camp Half-Blood, dealing with the supposed death of his mother, and accepting a fantastic set of beliefs.
Percy Jackson and the Lightning Thief explores Percy Jackson's journey to find his roots and live within the society of the Greek gods, demigods, and other mythical characters. In Chapter 5, "I Play Pinochle with a Horse," Percy has just de-horned the minotaur and wakes injured, being nursed back to health by a girl who is later revealed to be Annabeth.
When he leaves the clinic, he thinks of his mother and mourns her. (Though she's not dead, he believes she is at this point.) The beauty of the camp contrasts with the desolate feeling he has at the loss of his mother. But things happen quickly and Percy faces his second challenge.
Percy didn't know Camp Half-Blood existed. He wanders the camp, watching the kids do typical camp things. He has a difficult time understanding why he's there and what's going on. Instead of receding into a panic, he shows bravery as he continues on with Grover and then meets Chiron and Mr. D.
Percy's last challenge is accepting what Mr. D and Chiron tell him. Mr. D casually discusses the society of Greek gods and demi-gods as he plays pinochle. After he leaves, Chiron explains the situation more clearly. He points out elements of the Greek pantheon which appear in America, where the gods and goddesses now reside. Percy is disbelieving, but it explains everything that's happened to him recently which helps him not dismiss it outright. At the end of the chapter, Percy finds out that Chiron is a centaur.