Which of the following is a characteristic of real gases?

Real gases exhibit intermolecular forces, which is a hallmark of their behavior that distinguishes them from ideal gases. While ideal gas behavior assumes that gas molecules are point particles with no volume and do not exert any attractive or repulsive forces on one another, real gases do indeed have finite molecular size and experience intermolecular attractions. These forces can influence the gas's properties, particularly at high pressures and low temperatures, where the interactions between gas molecules become significant.

Intermolecular forces can lead to deviations from expected behavior based on the ideal gas law, especially in conditions that favor condensation or liquefaction of the gas. This understanding helps in predicting the behavior of gases under various conditions, explaining why real gases do not behave perfectly according to the ideal gas law.

In contrast to this characteristic, real gases do have volume (contradicting the first choice), and while they might obey Boyle's law (pressure and volume relationship) under certain conditions, they do not do so strictly in all scenarios, especially at low temperatures where deviations occur. The notion of a constant temperature is primarily related to isothermal processes, but it isn’t a defining feature of gases themselves—real gases can experience temperature changes.