In which type of stage change does no transfer of heat occur with the system?

The correct answer is adiabatic, which is defined as a process in which no heat is transferred to or from the system. In an adiabatic process, the system is thermally insulated from its surroundings, meaning that any changes in the energy of the system happen without any heat exchange. This can occur in processes where, for instance, a gas is compressed or expanded rapidly, leading to a change in temperature due to work done on or by the system rather than heat exchange.

In contrast, an isothermal process involves heat transfer, as it occurs at a constant temperature where heat enters or leaves the system to maintain that temperature. A phase change refers specifically to transitions between different states of matter (like solid to liquid) and typically involves heat transfer (latent heat) to accomplish this transformation. The term thermal generally relates to heat but does not describe a specific thermodynamic process related to heat transfer. Therefore, the adiabatic process distinctly characterizes the absence of heat transfer during the system's changes.