During condensation, what must be changed, temperature or heat energy?

Temperature.

Google, my dear Watson. It's your friend.

Nope, condensation occurs at constant temperature, and the heat content of the vapor has been reduced.

During condensation, heat energy must be changed.

During the process of condensation, it is the heat energy that must be changed, not the temperature. Condensation occurs when a gas or vapor cools down and loses heat energy, resulting in the transformation of the gas into a liquid state. This heat energy is released from the gas and absorbed by the surroundings, causing the gas molecules to slow down, come closer together, and form liquid droplets. Therefore, it is the transfer of heat energy that is essential for condensation to take place, rather than a change in temperature.