We report results from laboratory experiments of 10 keV electron irradiation of thin ice films of water and short‐chain hydrocarbons at ∼10−8 Torr and temperatures ranging from 70–100 K. Hydrocarbon mixtures include water with C3H8, C3H6, C4H10 (butane and isobutane), and C4H8, (1‐butene and cis/trans‐2‐butene). The double bonds of the alkenes in our initial mixtures were rapidly destroyed or converted to single carbon bonds, covalent bonds with hydrogen, bonds with −OH (hydroxyl), bonds with oxygen (C‐O), or double bonds with oxygen (carbonyl). Spectra resulting from irradiation of alkane and alkene ices are largely indistinguishable; the initial differences in film composition are destroyed and the resulting mixture includes long‐chain, branched aliphatics, aldehydes, ketones, esters, and alcohols. Methane was observed as a product during radiolysis but CO was largely absent. We find that while some of the carbon is oxidized and lost to CO2 formation, some carbon is sequestered into highly refractory, long‐chain aliphatic compounds that remain as a thin residue even after the ice film has been raised to standard temperature and pressure. We conclude that the high availability of hydrogen in our experiments leads to the formation of the formyl radical which then serves as the precursor for formaldehyde and polymerization of longer hydrocarbon chains.