Making Qualitative Predictions about AS

It is usually not difficult to estimate qualitatively how the entropy of a system changes during a simple process. As noted earlier, an increase in either the temperature or the volume of a system leads to an increase in the number of microstates, and hence an increase in the entropy. One more factor that correlates with number of microstates is the number of independently moving particles. 

We can usually make qualitative predictions about entropy changes by focusing on these factors. For example, when water vaporizes, the molecules spread out into a larger volume. Because they occupy a larger volume, there is an increase in their freedom of motion, giving rise to a greater number of possible microstates, and hence an increase in entropy. 

In which phase are water molecules least able to have rotational motion  

crystalline structure Motion restricted to vibration only Smallest number of microstates 

What major factor leads to a decrease in entropy as this reaction takes place  

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