Polarity

Polarity is determined by how the electrons are placed throughout the molecule.  Molecules can be either polar or non-polar.  Non-polar molecules are those which have an equal distribution of charges throughout the molecule making it symmetrical.  While polar molecules on the other hand are the exact opposite and have an unequal distribution of electrons. Propane is a non-polar molecule.  The picture below illustrates that the hydrogens are placed symmetrically around the carbons.

NOTE: Because the electronegativity values in Hydrogen are less than that in Carbon, there should be arrows from the H pointing towards the C.