How does the shape of a molecule affect the polarity of the molecule

The shape of a molecule affects polarity because of how bond dipoles between two atoms is affected by other atoms in the molecule. Bond dipoles are vector quantities (which means they have magnitude and direction), so when a molecule has two or more bond dipoles they can cancel each other out if they perfectly oppose each other. For example CO2 (O=C=O) has two dipole bonds, but since they equaly oppose each other they cancel out and the molecule is nonpolar. In bent molecules like H2O, the two hydrogens bonded to the oxygen have equal dipole moments, but they do not directly oppose each other so they do not cancel out. As a result the molecule is polar. So in summary the molecule's geometry affects the polarity of the molecule by dictating the direction of the vector quantities of the dipole bonds, which determines whether they will be able to cancel each other out (nonpolar) or allow for non zero dipole moments (polar).

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.