How is the tension in the relationship between Elizabeth and John Proctor evident in The Crucible?

The tension between John and Elizabeth Proctor becomes evident in Act II.  Early in this act, John tells his wife, "I mean to please you, Elizabeth," and she replies, "I know it, John," but "it is hard [for her] to say," according to the stage direction.  Then, when John moves to kiss her, she merely "receives it" but does not kiss him back.  He is visibly disappointed.  The fact that it is difficult for Elizabeth to acknowledge that her husband is making an effort to make her happy is telling, and her inability (or unwillingness) to return his affectionate touches is also a major clue that all is not well in their relationship. 
A few moments later, John asks her if she is "sad again" and though "she doesn't want friction," according to stage direction, "she must" voice her concerns and suspicions about his whereabouts that evening.  That Elizabeth anticipates "friction" means that there must have been a good deal of it lately, as well.  Further, the narrator tells us that "A sense of their separation rises" up between them.  There seems to be a wide gulf between them as the scene continues: John is caught in a small lie, and Elizabeth grows instantly suspicious of him; he is angered by her suspicion, and the tension grows.