Isothermal and Adiabatic Process

An endless number of resources may be used to learn the difference between isothermal and adiabatic processes. Any introductory physics literature or lecture, an online resource, or even a YouTube video can serve as a starting point for understanding the basic concept about both of them. Although these two processes are commonly mistaken for one another, there are legitimate grounds over which this confusion might occur. This misinterpretation arises from various incorrect assumptions about the subject matter.

Isothermal Process and Adiabatic Process

 The term “isothermal” refers to a state of constant temperature. As a result, every thermodynamic process that takes place at a constant temperature is called isothermal. In contrast, an adiabatic process is one in which no heat is exchanged with the object or system under consideration. If there is no heat exchange with an isolated system, does that indicate its temperature is constant? This is the most prevalent mistake. Also, as no heat was transferred, some people might just say that the temperature will remain constant.

Some different examples

(a) Suppose you keep a 0°C ice cube at the desk and simply keep an eye on it because it melts to emerge as 0°C water. For the ice cube, that became an isothermal technique due to the fact that its temperature did not change at all; instead, it went from strong to liquid form. But we need to know that to melt, it needs to take heat from the surroundings like the desk and the air – so the process is no longer an Adiabatic Process.

(b) Suppose you put an ice cube right into the bowl containing hot water; however, the bowl is an ideal thermal insulator. The ice cube melts, and the cold water also gets heated as the hot water cools. So this method isn’t ideally isothermal for both the ice and the water. But the equilibrium of ice and water did now no longer take in or provide off any heat due to the fact the bowl became an ideal insulator. If you take it in that sense, the process becomes adiabatic.

But the problem comes up most usually with appreciation to thermodynamic approaches on ideal gasses. That is, do not forget a piston-cylinder with a contained ideal gas. The character of that gas may be represented on a PV diagram – that means a graph of the pressure of the gas with respect to its volume.

Now let’s not forget instances in which the gas is moved from a smaller volume to a bigger one while the piston of the container moves ‘outward’. Such a process can be seen in numerous conditions. That is, the pressure may be held regular by including heat in the device because the volume will increase, and with a purpose to additionally increase the temperature. But the two instances you need to describe, due to the fact that the majority of confusion takes place, are an isothermal expansion and an adiabatic expansion.

Isothermal expansion

If the volume expands even if heat is being always provided to the contained gas in such a way as to maintain the temperature constant, it is referred to as isothermal. But through the correct gas law, pV=nRT, if the temperature is constant, and volume will increase while the pressure has to concurrently lower.

But if the temperature is also constant, this process will additionally ensure that the internal energy of the gas is constantly the same because the temperature is a measure of the internal energy of an ideal gas. But because the volume changed (increased), there has been work done by the gas in creating enough pressure to push the piston outward, so the foremost regulation of thermodynamics required that some heat be furnished to account for the quantity of work done. So heat is absorbed. Thus the work is done by the gas, and there has been no change in the internal energy of the system.

Adiabatic expansion

If the change in volume is equal to this problem and no heat has been exchanged, it would be, by definition, adiabatic. But because obviously gas might have done some work in opposition to the piston in this expansion, that energy might have been drawn from somewhere. If there has been no heat introduced to the environment, unlike isothermal expansion, the most obvious supply of power is the internal energy of the gas itself. Therefore, in the adiabatic expansion, there might be a fall in internal energy. Now, this intended a drop in temperature and results in an extra drop in pressure which occurred at some point of the above isothermal expansion. So no heat was absorbed, work is simply done by the gas, and the internal energy of the gas is exhausted, which means the temperature also dropped.

Both strategies can easily be displayed on a pressure-volume diagram like this:

The most common confusion between the two processes is -fold. They appear comparable when displayed on a pressure-volume diagram if it isn’t made clear that one technique follows an isotherm and the opposite drops from a better temperature isotherm to a decreased one. One of the other most common confusion has to do with the occasionally imprecise use of the phrases heat, temperature, and internal energy. Temperature measures internal energy; heat is a switch of thermal energy. Zero heat switch does now no longer suggest steady temperature. There is a totally easy example of better understanding that distinguishes between an almost isothermal process and an almost adiabatic one: Place your hand right in front of your mouth and blow air on your palm. You can do it in two different ways:

(a) If your mouth is wide open, you sense hot air. Of course, the air is coming out of your lungs at your body temperature – and your outer temperature is slightly lower than that. That is a situation near to an isothermal expansion because the air escapes – and also you sense the warm air.

(b) Now, don’t wide open your mouth; make a small “O” by your lips. So the air comes out via a small hole. Now blow air out. That air feels cool. Do you understand why? Obviously, your lips didn’t cool it off. The answer to this question is that by coming via a small opening that air expands rapidly. In that short expansion, it pushes the air out of the manner. The power to do this work in opposition to the environment is drawn here from its own internal energy – so the temperature dropped. And you feel that the air coming out of your mouth is cool.

The Difference between the Isothermal and Adiabatic Process

Isothermal Process

1. In an isothermal process, the temperature of the system remains constant.

2. In this process, the system exchanges heat with the surroundings.

3. The total internal energy of the system remains constant (DE = 0).

4. In this process, the system is not thermally isolated.

5. This process can be made reversible.

6. In this process, Q = W  as DE=0,

Adiabatic Process

• In an adiabatic process, the temperature of the system changes

• In this process, the system does not exchange any heat with the surroundings

• Total internal energy (DE) of the entire system changes

• The total heat content of the system remains fixed (DH = 0)

• In this process, the environment, as well as the system, is thermally isolated

• This process cannot be made reversed

• In this process. W = (-) DE as DQ=0

Conclusion

While in a process, if the system exchanges heat with the surroundings to feel the temperature constant, such processes are called the Isothermal Process. Whereas if no heat is exchanged, the temp is not constant, which makes the process an Adiabatic Process.