Question

Why are the boiling points of hexane, and heptane, different?

Answer 1

Though the same functional group is the same, longer is the molecule, more is the degree of interaction in the molecule which leads to the more boiling point. If a compound has more molecular weight, it also leads to a higher boiling point. Heptane is a longer molecule than hexane which leads to the higher boiling point.

Complete Step By Step Answer:
Chemical compounds are classified into functional groups based on the groups present in it. Alkanes, alkenes, and alkynes are the hydrocarbons consisting of only carbon and hydrogen atoms. Out of which alkanes are the only saturated hydrocarbons.
Alkanes are the saturated hydrocarbons with the general molecular formula of ${C_n}{H_{2n + 2}}$ , where n is the number of carbon atoms.
Hexane, and heptane are the alkanes that consist of six, and seven carbon atoms. These both chemical compounds belong to the same functional group i.e.. alkanes. But there was an extra methylene group in heptane than hexane.
Longer is the molecule, more will be the degree between the interaction of molecules. Higher will be the boiling point. Thus, heptane has a higher boiling point than hexane.
Thus, due to the greater number of groups in heptane leads to the difference in boiling points of hexane and heptane.

Note:
The molecular formula of hexane is ${C_6}{H_{14}}$ , and the molecular formula of heptane is ${C_7}{H_{16}}$ . There were a greater number of groups in heptane than hexane, which means heptane is the longest hydrocarbon molecule than hexane.