Answer
Alkanes participate mainly in substitution reaction. In substitution reaction one atom or a group of atoms is replaced by another one. So, there is no disruption in carbon skeleton after replacement. The nature of bond remains same after substitution. This happens for alkanes when they participate in substitution reaction.
But, Alkanes mainly participate in addition reaction. In addition reaction two atoms or group of atoms are attached with C atoms which are associated with double bonds (for alkene). So, after addition of atoms to Alkene, the double bond breaks and becomes single bond therefore disrupting the carbon skeleton of parent molecule.
Work Step by Step
Below are the example of reaction of alkane (substitution reaction) and reaction of alkene (addition reaction).
