Final answer:
Evaporation is the stage where liquid water turns into water vapor, while condensation is the stage where water vapor turns back into liquid, forming clouds.
Step-by-step explanation:
The stage of the hydrologic cycle that involves changing liquid to water vapor is called evaporation. This process occurs when heat energy from the sun causes liquid water to turn into water vapor. Water evaporates from various sources like oceans, lakes, rivers, and even plants through a process called transpiration.
The stage of the hydrologic cycle that involves changing water vapor to liquid is called condensation. This occurs when water vapor cools and turns back into liquid, forming clouds in the atmosphere. Eventually, the condensed water droplets join together and fall to the Earth's surface as precipitation in the form of rain, snow, or hail.