Many exciting moments occur in A Raisin in the Sun, though not all of them are exciting in that they are positive, rather they are exciting because they are dramatic.
For example, the author, Lorraine Hansbury, begins to develop the conflict in Act I, scene ii when Walter comes home and asks his mother, Mrs. Younger, for money to invest in a liquor store with his friend Willy Harris. Walter's mother and wife, Ruth, both know that this is another "get rich quick" scheme and that it is unlikely to pan out. Walter's mother would rather invest the money more responsibly and refuses to give Walter a share to put into what she thinks is a sinful business.
The scene becomes heated rather quickly. Walter feels he is being emasculated (not respected as a man). His mother feels like she is doing what is best for the family. Mean while, Ruth has just come back from a consultation with an abortion doctor. She is pregnant and afraid that her and Walter will not have enough money to care for the newborn child.
The whole scene explodes when Walter threatens to go out drinking again and Ruth tries to go with him. He tells his wife he doesn't want her near him and he storms out of the house leaving his wife in despair. As he leaves, his mother tells him he is a disgrace to his dead father's name.
Exciting? Absolutely. The drama keeps the audience on the edges of their seats.