Which of the following is a physical property of alkanes?

The choice that identifies a physical property of alkanes accurately highlights that the boiling point of alkanes increases with molecular weight. This is primarily due to the increasing number of carbon and hydrogen atoms in larger alkane molecules, which leads to greater van der Waals forces (a type of intermolecular attraction). As the alkane's molecular weight rises, the overall size of the molecules increases, thereby enhancing these weak interactions. Consequently, more energy (in the form of heat) is required to overcome these forces during the transition from liquid to gas, resulting in a higher boiling point.

Other options may carry some facts about alkanes but do not accurately represent their typical physical properties. For instance, alkanes are generally insoluble in water but are actually soluble in nonpolar solvents, contradicting any statement about their solubility. Furthermore, while alkanes may have a density that could be higher compared to some other organic compounds, they do not have the highest density overall in the realm of organic chemistry. Lastly, their melting points are influenced by various factors, and while they can be higher compared to alkenes with the same number of carbon atoms, this is not a definitive characteristic of alkanes across the board. Thus,