Explain the reactivity of alkenes.

(N/A) Alkenes contain a carbon-carbon double bond,which consists of one strong $\sigma$-bond and one weak $\pi$-bond.
The $\pi$-electrons are loosely held and are available as a source of electron density,making the $\pi$-bond a site of high electron density.
Due to this,electrophiles $(E^+)$ can easily attack the $\pi$-bond,leading to its cleavage and the formation of two new $\sigma$-bonds in an addition reaction.
Consequently,alkenes are more reactive than alkanes towards electrophilic addition reactions.
Note: The bond enthalpy of a $C-C$ single bond in alkanes is approximately $348 \ kJ \ mol^{-1}$,while the total bond enthalpy of a $C=C$ double bond in alkenes is approximately $610 \ kJ \ mol^{-1}$ (the $\pi$-bond itself is weaker than the $\sigma$-bond).