i don't think pentene is polar.
if you're talking about polarity in relation to molecules, not bonding, then remember something about the symmetry of a molecule? if the charges cancel each other out then it's non-polar. or something that was years ago '-_-
you can make the approximation that a carbon-hydrogen bond is non-polar, why? well the EN value of carbon is 2 and hydrogen is usually given as 2.2, hence not much of a difference, and just about all the C- H bonds encountered in HSC belong to linear hydrocarbons, which due to their good looking symmetry, contribute further to the overall non-polar nature of C-H bonds in molecules