Final answer:
Gravitational potential energy was converted into kinetic energy and caused the temperature to rise. Through collisions, this kinetic energy thermalized, generating a hot ball of gas that eventually formed a star.
Step-by-step explanation:
As the nebula collapsed, gravitational potential energy was converted into kinetic energy and caused the temperature to rise.
The gravitational potential energy of the collapsing material was transformed into the kinetic energy of the gas particles as they raced toward the center of the cloud.
Through collisions, this kinetic energy thermalized, generating a hot ball of gas that eventually formed a star.