What is the conversion of a liquid into the gaseous state through the action of heat?

Vaporization is the correct term for the conversion of a liquid into a gaseous state through the action of heat. This process encompasses both evaporation and boiling, with evaporation occurring at the surface of the liquid at any temperature, while boiling happens when the liquid reaches its boiling point. Vaporization is a broader term that includes both of these processes.

Other choices, while related to changes in states of matter, do not accurately define the conversion of liquid to gas. Evaporation specifically refers to the transformation at the liquid's surface without needing to reach the boiling point. Condensation is the opposite process, where gas transitions to a liquid state. Sublimation involves a solid changing directly into a gas, bypassing the liquid state altogether. Understanding these distinctions is crucial in grasping the principles of phase changes in substances.