MadSci Network: Physics
Query:

Re: Freezing of Water versus Alcohol

Area: Physics
Posted By: Mark Andress, Analytical Chemist, Industry, Abbott Labs
Date: Fri Sep 19 12:07:29 1997
Area of science: Physics
ID: 874001181.Ph
Message:
The easy answer to your question is because alcohol's freezing point is 
-117 degrees and water's freezing point is 0 degrees.  Your refrigerator 
doesn't get cold enough to freeze alcohol.

A better answer is motion.  A solid has very little motion of the 
molecules.  As the heat is raised, the amount of motion increases.  
Eventually, the motion is large enough for the transition to a 
liquid to occur.

You would think that the size of the molecule would influence the freezing 
point temperature.  And generally, it does.  So why does alcohol, with a 
molecular wt of 46, freeze at a lower temperature than water, which has a 
molecular wt of 18? Another factor comes into play.  This factor is called 
hydrogen bonding.  It causes an increased attraction between molecules 
which makes them harder to separate(or put into motion).  This raises the 
freezing point.

I hope this quick explanation helps.   

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