Final answer:
The process of a liquid turning into a gas is called evaporation, which is a phase change occurring at the surface of a liquid at various temperatures.
Step-by-step explanation:
The process of a liquid becoming a gas is called evaporation. Evaporation can occur at various temperatures and is a common phase change where a liquid gradually turns into a gas at its surface without boiling. For example, when water in a puddle slowly disappears over time, it is evaporating into the atmosphere. In contrast to evaporation, other phase changes include freezing, where a liquid becomes a solid; sublimation, the transition from a solid directly to a gas; and melting, the process of a solid becoming a liquid. Therefore, the correct answer to the question is option 2) Evaporation.