# Thermal equilibrium versus pressures

• intervoxel
In summary, the concept of pressure in a closed system is based on the average force per unit area from atoms, which can result in random fluctuations. As the system size increases, these deviations become smaller and are essentially unmeasurable on a human scale. It is not necessary for the system to have been in thermal equilibrium when it consisted of a single region of uniform pressure, and it is possible for regions with different pressures to have existed in the past due to atomic motion and temperature differences.
intervoxel
Is it possible for a closed system in thermal equilibrium possesses two regions with different pressures supposing such regions had the same pressure in the past?

It's required by atomic theory and thermodynamics. "Pressure" is just the average force per unit area from the bombardment of vast numbers of atoms; thus, random fluctuations are inevitable. Two regions of equal pressure at one instant can hardly avoid having different pressures at the next instant, due to atomic motion. The larger the system, however, the smaller the deviations from the average value. On the human scale, these deviations are essentially unmeasurable.

Does the question require that the system was in thermal equilibrium when it consisted of a single region of uniform pressure?

No, it is supposed they had different temperatures in the past.

## 1. What is thermal equilibrium?

Thermal equilibrium refers to a state in which two systems that are in contact with each other have reached the same temperature and there is no net transfer of heat between them.

## 2. How is thermal equilibrium related to pressure?

In thermal equilibrium, the pressure of the two systems will also be equal. This is because the particles in each system are moving at the same average speed, resulting in the same force being exerted on the walls of the container.

## 3. What happens to pressure when thermal equilibrium is reached?

When thermal equilibrium is reached, the pressure of the two systems will be equalized. This means that if one system had a higher pressure initially, it will decrease to match the pressure of the other system.

## 4. How does temperature affect the pressure of a system?

As temperature increases, the average speed of particles in a system also increases. This results in more collisions between the particles and the walls of the container, leading to an increase in pressure.

## 5. Can two systems be in thermal equilibrium at different pressures?

No, two systems in thermal equilibrium must have equal pressures. If the pressures are different, then heat will continue to transfer between the systems until thermal equilibrium is reached and the pressures are equalized.

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