How to distinguish between polar and non-polar molecules/compound? for instance, one that you have not studied before but have to know if its polar or non-polar. can you distinguish it from the basic structure of the molecule?

a molecule is polar if we find electronegativity differences between two differing atoms.
when there is large difference between electronegativity values, the more polar the molecule is.
 when  the electrons are shared equally between the nuclei.then the molecule is non polar
  in Cl2 moleculethere is no  no polar bonds because the electron charge is  same on both atoms.
 It is therefore a nonpolar molecule.
bonds in hydrocarbon molecules,  as hexane, C6H14, are polar, 

The gas would begin to expand, and eventually the can would burst or explode.

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .