What happens during a phase change from liquid to gas?

During a phase change from liquid to gas, vaporization occurs as the liquid absorbs energy, which allows the molecules to escape into the gas phase. This process requires energy input, typically in the form of heat, to overcome the intermolecular forces that hold the liquid molecules together.

As the liquid vaporizes, it does not gain temperature in a linear fashion; rather, the temperature remains constant until all of the liquid has transitioned into gas. Therefore, the option regarding temperature increase is not applicable during this phase change.

Moreover, the substance does not lose energy; instead, it gains energy to facilitate the transition from one phase to the other. Regarding density, gases are typically less dense than liquids, so the substance does not increase in density; instead, it decreases in density during this process. Thus, the correct option reflects the process of phase transition, highlighting vaporization as the essential characteristic of the liquid-to-gas change.