Final answer:
The boiling points of alkenes increase with the length of their carbon chains due to stronger dispersion forces. Alkenes are named by identifying the longest chain containing the double or triple bond and giving that bond the lowest possible number. Straight-chain alkanes have higher boiling points than branched ones due to differences in intermolecular interactions.
Step-by-step explanation:
The study of the boiling points of alkenes as a function of carbon chain length shows that as the length of the carbon chain increases, the boiling point also tends to increase. This is due to the enhanced London dispersion forces present in longer chains, which in turn increases the intermolecular attractive forces. Therefore, a graph that represents an upward trend as the number of carbons in the chain increases would best represent the trend for the boiling point of alkenes. When naming alkenes and alkynes, one must identify the longest chain containing the double or triple bond and assign the lowest possible number to this bond.
In terms of geometry, alkanes are long and cylindrical, and with increasing molar mass, their boiling points increase. However, alkanes with branching have spheres that result in less surface contact between the molecules and hence lower boiling points compared to their straight-chain counterparts.
The naming of hydrocarbons such as alkenes and alkynes involves finding the longest continuous chain of carbon atoms which determines the parent name, and numbering the chain such that the double or triple bond receives the lowest possible number. For example, in a molecule with eight carbon atoms, the parent hydrocarbon is octane.