Thermal Expansion The thermal expansion of an object is a consequence of the change in the average separation between its constituent atoms or molecules At ordinary temperatures, molecules vibrate with a small amplitude As temperature increases the amplitude increases This causes the overall object as a whole to expand Reeder-05-06 Physics 201: Lecture 22, Pg 11Reeder - 05-06 Physics 201: Lecture 22, Pg 11 Thermal Expansion The thermal expansion of an object is a consequence of the change in the average separation between its constituent atoms or molecules At ordinary temperatures, molecules vibrate with a small amplitude As temperature increases, the amplitude increases This causes the overall object as a whole to expand