How do chapters 5 and 6 start? What is the effect?

Both chapters open in similar ways, setting the scene with description and then locating Lennie in the scene. In chapter five, Steinbeck describes the peaceful quiet of a Sunday afternoon with the light shining in through slats of the barn. We realize that Lennie is alone here, with the other men outside playing horseshoes. The four-taloned Jackson fork dangling overhead produces a slight sense of menace. The feeling of foreboding grows as the "camera," so to speak, zooms in on a worried Lennie with dead puppy.
Chapter six also begins with description of a peaceful, quiet scene, this time back at the pond where Lennie and George first started. Again, a sense of foreboding is established as we watch a heron catch and eat a snake. Lennie appears as a natural creature, coming up to the pool like a "creeping bear" and drinking water. As in chapter five, he is worried that George will be angry with him.
The effect of both openings is to set Lennie apart, associating him more with animals, creatures of nature, than other human beings. Both openings, despite the peaceful, quiet settings, raise a sense of unease about what is going to happen to Lennie.