• Undoubtedly0

#### Undoubtedly0

In Principles of General Thermodynamics, Hatsopoulus and Keenan (p 442) make the following claim:
if a system is in such a state that it cannot receive work adiabatically, it is in equilibrium.
What, however, would be some physical examples of such a system?

A piston with ideal gas as a working fluid in thermal equilibrium with an infinite reservoir. If you do constant pressure compression work on the piston, the gas gets colder, so there's an irreversible flow of heat into the cylinder from the reservoir. The opposite is true if you do expansion work. Either way, doing work on the system results in heat flow in/out of the system in an irreversible manner. The irreversibility is the key to understanding this claim. Remember that thermodynamic equilibrium is a state of maximum entropy.

## 1. What is an adiabatic process?

An adiabatic process is a thermodynamic process in which there is no transfer of heat or matter between the system and its surroundings. This means that the system is completely isolated, and the only way for it to exchange energy is through work.

Some systems cannot receive work adiabatically because they are not completely isolated. These systems may have some form of energy transfer, such as heat or matter exchange, with their surroundings, which prevents them from undergoing an adiabatic process.

## 3. What are some examples of systems that cannot receive work adiabatically?

Examples of systems that cannot receive work adiabatically include open systems, such as a pot of boiling water, where heat and steam can escape, and closed systems with imperfect insulation, such as a refrigerator.

## 4. How does an adiabatic process affect the internal energy of a system?

In an adiabatic process, there is no transfer of heat or matter, so the internal energy of the system remains constant. This means that any changes in the system's energy must come from work done on or by the system.

## 5. Can an adiabatic process occur in real-world systems?

Although ideal adiabatic processes do not occur in real-world systems, they can be approximated in certain situations. For example, a well-insulated thermos can come close to an adiabatic process, as it minimizes heat transfer with the outside environment.