How does the number of bonds in a carbon chain affect its melting and boiling points?

Answer 1

given the same number of bonds?

the double bonds, and triple bonds are very easily broken, as compared to the C-H bonds.

http://www.engineeringtoolbox.com/fuels-boiling-point-d_936.html

compare pentane, and pentene, butane, and butylene.

Answer 2

The length of a carbon chain has more to do with melting and boiling points than the number of bonds. Double bonds tend to lower the melting point if the chain is in a "cis-" configuration. As BobPursley pointed out, the question is not clear enough for a definite answer.