Why does crystallization of a solute occur

Atoms or ions of solute leave solution during the process of crystallization to form a regular repeat lattice. 

The extent of solute disorder is high before crystallization, because each ion or molecule resides in solution, and thereby experiences the same freedom as a molecule of liquid. Conversely, the extent of disorder after crystallization will inevitably be much smaller, since solute is incorporated within a solid comprising a regular repeat lattice. 

The value of AS can only be negative because the symbol A means final state minus initial state , and the extent of disorder during crystallization clearly follows the order solute disorder(initiai) solute disordering) . We see how the extent of disorder in the solute decreases during crystallization in consequence of forming a lattice and, therefore, do not expect crystallization to be a spontaneous process. 

But crystallization does occur, causing us to ask, Why does crystallization occur even though AS for the process is negative  

To answer this question, we must consider all energetic considerations occurring during the process of crystallization, possibly including phenomena not directly related to the actual processes inside the beaker. 

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