$
\mathrm{C}_2 \mathrm{H}_6 \stackrel{4500^{\circ} \mathrm{C}}{\longrightarrow} \mathrm{C}_2 \mathrm{H}_4+\mathrm{H}_2
$
Above reaction is called as
combustion
rearrangement
pyrolysis
cleavage
Solution
Decomposition of a compound by application of heat is called pyrolysis and pyrolysis of higher alkanes into a mixture of lower alkanes, alkenes, etc. is also called cracking.