ya she. but to find polarity you have to draw the molecule and find the shape (molecular geometry), then you compare the elctronegativities. For example, for H2O the shape is... bent planar. so then comapre the elctronegatives and you will see that the Oxygen is more electronegative and is thus more "negative" than the relatively positive Hydrogens. Thus, it is polar. For another compound such as AlH3, the molecule is a trigonal planar.
Thus, no matter what, it will not be polar because the charge will be distributed in no one direction.
For Aspirin it would be more complicated since it has no single shape.
Also, when aspirin hits acid pH in the stomach it actually can lose a hydrogen which can change the polarity to become more soluable. Since aspirin is polar in some spots, primarily the O bonds, its slightly soluable in water. C-H bonds are only slightly polar.