The tone of chapter two of Animal Farm is twofold. First, there is a sense of sadness, as Old Major dies. Second, there is a sense of anticipation in chapter two as well, because the animals are preparing for the revolution and succeed by the end of the chapter.
In fact, the rebellion comes much faster than any of the animals thought, because Mr. Jones begins to drink excessively presumably to drown his sorrows from losing a lawsuit. He, therefore, neglects the farm. When this happens, the cows break into the store in hunger, and they begin to eat. When the men on the farm see this, they try to stop things, but this causes the revolution to gain momentum.
The animals are successful. In light of this, the animals are looking forward to a new life on the farm. Anticipation is in the air.