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    | • | A molecule is
    polar if its centers of positive and 
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    |  | 
   
    |  | negative charges
    do not coincide. If a molecule is 
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    |  | 
   
    |  | polar we say that
    it acts as a dipole. In an electric 
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    |  | 
   
    |  | field nonpolar
    molecules (positive and negative 
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    |  | 
   
    |  | centers
    coincide)  do not align with the
    field but 
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    |  | 
   
    |  | polar molecules
    do. 
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    |  | 
   
    | • | Next we will see
    why this happens and the 
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    |  | 
   
    |  | implications. 
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