Which of these processes is characterized by no heat exchange with surroundings?

The process characterized by no heat exchange with the surroundings is known as adiabatic. In an adiabatic process, the system is insulated from its environment in such a way that any change in internal energy comes entirely from work done on or by the system, rather than from heat transfer. This means that during an adiabatic transformation, the temperature may change solely because of work performed on or by the gas, without any energy being added or removed in the form of heat.

In contrast, other processes define different types of constraints. Isothermal processes occur at a constant temperature, which implies that heat is exchanged with the surroundings to maintain that constant temperature, despite any work being done. Isobaric processes take place under constant pressure, allowing heat to flow in or out to maintain pressure, while isochoric processes happen at constant volume, where no work is done and heat can also be exchanged, though the system's volume remains unchanged. Each of these processes involves heat exchange in some form, making them fundamentally different from the adiabatic process.