Vacuum Expansion: Understanding the Final States of Closed Systems

In summary, the conversation discusses two closed systems, one involving a free expansion of a gas into a vacuum and the other involving a piston with the same gas on one side and a vacuum on the other side. The final difference of states between the systems after equilibrium is the same, as the work done by the gas on the piston is converted into kinetic energy and eventually into heat, resulting in the same state for both systems.
  • #1
Chuck St. Lou
24
0
I have uploaded a diagram of two closed systems in which no work can or heat can be leave the system (See attached file). One is a free expansion of a gas into a vacuum and the other is a piston with the same gas on one side and a vacuum on the other side. After the piston is released and is pushed by the gas to the vacuum side what is the final difference of states of each system after equilibrium?
 

Attachments

  • Free expansion.JPG
    Free expansion.JPG
    43.2 KB · Views: 460
Physics news on Phys.org
  • #2
There's no difference between the two systems. If this is a follow-up to https://www.physicsforums.com/showthread.php?t=288946", note that the posters there were assuming that the piston was attached to the outside world and that energy was being removed in the form of work.
 
Last edited by a moderator:
  • #3
The state will be the same, eventually. The reason is that your perfect piston will be *accelerated* by the force done by the gas on the piston. The work of the gas on the piston will be transformed into kinetic energy of the piston.

Now, or your piston is *really* perfect, and will hence collide elastically on the wall, and bounce back, recompressing the gas to its original volume V1, and expand again, and bounce back, and so forth,...

Or you will allow for some dissipation (be it in the form of *sound* and vibrations) due to this movement of the piston. It can also be that after the first expansion, the piston is *glued* to the wall, in which case its kinetic energy is dissipated as heat into the glue who did the braking.

In any case, the work done on the piston is converted into heat again, and given back to the gas (assuming negligible heat capacity of the piston itself).
 

1. What is vacuum expansion?

Vacuum expansion is a process in which a closed system, such as a container or chamber, is rapidly emptied of its contents, creating a vacuum. This can occur naturally, such as when air is removed from a sealed bag, or it can be achieved through mechanical means, such as with a vacuum pump.

2. Why is vacuum expansion important?

Understanding vacuum expansion is important in many scientific and technical fields. It can help us understand the behavior of gases and fluids in closed systems, as well as the effects of pressure differentials. It also has practical applications, such as in the creation of vacuum-sealed packaging and the operation of vacuum-based technologies like vacuum tubes and vacuum pumps.

3. How does vacuum expansion affect the final states of closed systems?

Vacuum expansion can have a significant impact on the final state of a closed system. As the pressure decreases, the volume of the system increases, which can lead to changes in temperature, density, and other properties. In some cases, the final state may be a complete vacuum, while in others, the system may reach a state of equilibrium with the surrounding environment.

4. What factors influence the outcome of vacuum expansion?

Several factors can influence the outcome of vacuum expansion, including the initial pressure and temperature of the system, the volume and shape of the container, and the rate at which the vacuum is created. The type of gas or fluid being expanded also plays a role, as different substances have varying properties and behaviors under different conditions.

5. How can vacuum expansion be measured and studied?

Vacuum expansion can be measured and studied using various techniques, such as pressure and temperature sensors, optical methods, and computational simulations. These methods allow scientists to observe and analyze the changes in the system's properties as it expands and reaches its final state. Additionally, experiments can be designed to manipulate different variables and observe their effects on the expansion process.

Similar threads

  • Other Physics Topics
Replies
14
Views
2K
Replies
22
Views
2K
Replies
5
Views
518
  • Other Physics Topics
Replies
2
Views
624
Replies
1
Views
964
Replies
8
Views
1K
  • Thermodynamics
Replies
2
Views
1K
Replies
5
Views
907
Replies
8
Views
1K
Replies
5
Views
517
Back
Top