The degrees of freedom associated with the atoms have changed. The greater the freedom of movement and the number of degrees of freedom, the greater the entropy of the system. Individual molecules have degrees of freedom associated with motions within the molecule. Vibrational motion . Rotational motion .
Energy is required to get a molecule to translate, vibrate, or rotate.
The entropy changes dramatically at a phase change. Gases are formed from solids or liquids. The number of gas molecules increases. The temperature is increased. 19.4 Calculation of Entropy Changes Absolute entropy can be determined from complicated measurements.