Final answer:
Unbranched (linear) compounds have stronger dispersion forces than unbranched isomers due to the greater surface area available for contact between molecules in linear compounds.
Step-by-step explanation:
Unbranched (linear) compounds have stronger dispersion forces than unbranched isomers. This is because of the greater surface area available for contact between molecules in the linear compounds, resulting in correspondingly stronger dispersion forces. On the other hand, unbranched isomers have a smaller surface area available for intermolecular contact, leading to weaker dispersion forces. For example, the boiling points of isomers n-pentane, isopentane, and neopentane differ due to the difference in their dispersion forces.