Which best describes the motion of pentane molecules in liquid phase?

Hydrocarbons may vary from state to state depending on the length of the carbon chain. For methane to butane, they are usually in gas form. Starting from pentane, they are in the liquid form. For very long carbon chains, that occur as solids. Now, it depends if the pentane is in a nonpolar liquid or polar liquid. Since pentane is nonpolar, it is miscible in the liquid solvent. The movements would most likely be free flowing. But if he solvent is polar, the molecules would repel with one another. In the end, it will form two liquid phases, on for the pentane and one for the polar solvent.