How does Steinbeck create tension in this chapter?

The setting and the content of Chapter Six, ultimately emphasize how much has changed since the novel's opening. Where George was once full of life - angry and forgiving - now he is a husk of himself, bereft of emotion as he goes through his monologues. What was once a plausible - if far-fetched - fantasy has disintegrated into delusion. He knows what must happen, even as Lennie goes on believing in the rabbits. Whereas in Chapter One we see George and Lennie's "best laid plans," here in Chapter Six we have irrefutable evidence that, just as Robert Burns' poem predicts, these plans have gone awry.