From Daniela Santos (Harris City Academy Crystal Palace)
I figured it would be possible for me to calculate the stability based on the strength of the total bonds within each of the isomers, the strongest isomers being the most stable. The bond values I discovered (and therefore used to calculate total bond strength) were as follows:
347 kJ/mol for a carbon-carbon single bond
611 kJ/mol for a carbon-carbon double bond
839 kJ/mol for a carbon-carbon triple bond
413 kJ/mol for a carbon-hydrogen bond
This means that isomer one has a total of 2957 kJ/mol in bonds, isomer two has 2874 kJ/mol in bonds and isomer three has a total of 2838 kJ/mol in bonds. In terms of stability, that would suggest that the first isomer was the most stable of the three as it has the highest bond strength, then the second and the third would be the least stable of the three.