[AdiDex]

I am confused ...!!!
That which one is more stable.....what will be the order of stability.….?? And why....?
2-butene (trans)

2-butene (cis)


Or
2-methyl propene

[Enthalpy]

You should have a big table of heats of formation at hand, because you'll probably need it more often.

• Some are available on the Internet. Keywords "Heat of formation", "enthalpy of formation" or "thermodynamic properties" combined with "chemical substances" or similar.
• The "CRC handbook of Chemistry and Physics" has such a table and must be available where people study chemistry.

Nist is sometimes helpful (= when free)
http://webbook.nist.gov/cgi/formula/C4H8
there you find the "Gas phase thermochemistry data" of the three gasses.