Chapters 9&10 give details of Chillingworth's physical appearance, and how his countenance seems to reflect the evil that is within him.
Chapters 11&12 give details of Dimmesdale's failing health. Ironically, as he grows physically weaker (the result of inward guilt), he grows outwardly more popular, and to his parishioners, more and more "pious."
Chapter 13 chronicles the first of Hester's major changes, both physically and emotionally. While she grows older (and less beautiful) on the outside, she grows wiser and more empathetic on the inside. Arguably, her beauty is moving inward.
Chapters 20 and 21 focus on the physical and emotional changes in both Hester and Dimmesdale, as in the forest they are allowed to really look earnestly at and talk to each other for the first time in many years.