The number of possible isomers increases rapidly as the length of the chain increases. These are called substituents. Alkanes, straight or branched chains, all have an exterior which is mostly hydrogen atoms. Surface of one molecule is quite like any other. Soluble in each other and in other non-polar solvents.
Alkanes are rather unreactive chemically.
Also are involved in substitution reactions. 2n, creates at least one pi bond. Has sp2 hybridization on the double bond. No rotation about the double bond, this leads to the formation of geometric isomers. Also can polymerize .