When ethane is heated to high temperature in absence of air or oxygen, it gives

 When the ethane is heated to high temperature in presence of Zn  is known as dehydrogenation.

Balanced chemical reaction

          ${\mathrm{C}}_2{\mathrm{H}}_6\stackrel{∆}{\to }{\mathrm{C}}_2{\mathrm{H}}_4+{\mathrm{H}}_2$

So, when ethane is heated to high temperature in absence of air or oxygen, it gives ${\mathrm{H}}_2\text{ and }{\mathrm{C}}_2{\mathrm{H}}_4$.