# What pressure not increases if I seal the container?

• Ravi Singh choudhary
It is defined by the force per unit area regardless of what is exerting that force.In first case; evaporation rate will become slower and more number of vapor will be above water surface. As diffusion of vapor is now stopped.In second case; I don't understand why pressure is same. What is the new force that come into play for creating same pressure.In first case; evaporation rate will become slower and more number of vapor will be above water surface. As diffusion of vapor is now stopped.

#### Ravi Singh choudhary

CASE1:
A container with some water is open to atmosphere, pressure is definitely atmospheric, no somehow I put cover over it and sealed it also. Pressure would increase because new equilibrium will establish between water and its vapour so pressure will increase in the closed container.

CASE2:
There is an empty container that means only air, now I cover it. Pressure will not increase; but my doubt is; as atmospheric pressure is defined as the weight of atmosphere over it divided by the surface area. As I close the container the weight is acting on the cover that load will be taken by the whole container so how the particles inside the container will feel the atmospheric pressure? Cover is not a fluid that means no pascals law; so how pressure reaches inside the container?

Ravi Singh choudhary said:
CASE1:
A container with some water is open to atmosphere, pressure is definitely atmospheric, no somehow I put cover over it and sealed it also. Pressure would increase because new equilibrium will establish between water and its vapour so pressure will increase in the closed container.
Before any hypothetical vapor is emitted from the surface of the sealed-in water, that water is under atmospheric pressure. It was at atmospheric pressure before it was sealed in so it will be at atmospheric pressure immediately after.

If any vapor were to come out, it would be under at least one atmosphere of pressure. But under one atmosphere of pressure, that vapor would be condensing. So no vapor can come out. So pressure remains at one atmosphere.
CASE2:
There is an empty container that means only air, now I cover it. Pressure will not increase; but my doubt is; as atmospheric pressure is defined as the weight of atmosphere over it divided by the surface area. As I close the container the weight is acting on the cover that load will be taken by the whole container so how the particles inside the container will feel the atmospheric pressure? Cover is not a fluid that means no pascals law; so how pressure reaches inside the container?
Pressure is not defined as the weight of atmosphere divided by surface area. It is defined as force per unit area regardless of what is exerting that force.

In first case; evaporation rate will become slower and more number of vapor will be above water surface. As diffusion of vapor is now stopped.

In second case; I don't understand why pressure is same. What is the new force that come into play for creating same pressure.

Ravi Singh choudhary said:
In first case; evaporation rate will become slower and more number of vapor will be above water surface. As diffusion of vapor is now stopped.
Did you seal it with zero head space or with some air-filled head space?

jbriggs444 said:
Did you seal it with zero head space or with some air-filled head space?

Ravi Singh choudhary said:
Oh, that makes sense then. Yes. If the head space is dry air then vapor can evaporate into the head space and increase the pressure within the container.

Ravi Singh choudhary
Help me in the second case

Ravi Singh choudhary said:
Help me in the second case
Boyle's law. If you start with enough gas in the container to maintain atmospheric pressure at its current temperature then closing the lid will not change that.

jbriggs444 said:
Boyle's law. If you start with enough gas in the container to maintain atmospheric pressure at its current temperature then closing the lid will not change that.
Didn't get you; sorry

Judging by the rapidity of your response, you did not Google Boyle's law. Accordingly, I will stop helping you.

Actually Sir, I know Boyle's law as follows; Pressure is inversely proportional to the volume, if temperature remains contant. But I was not able to relate this concept here

The volume of the chamber does not change just because you close the lid. Accordingly, the pressure does not change just because you close the lid.

Ravi Singh choudhary
I always used to relate atmospheric pressure due to weight of the air. What I understand atmosphere is hydrostatic that means each part of it is at 1atm; neglect pressure change due to height as density is low.

But something hollow solid container is placed in that sea of atmosphere and as solid will not follow pascal's law it, air inside the container will not experience the same pressure as outside. But here thermodynamics come into play. Due to isothermal condition. I think I am almost convinced but something is missing in my conceptualization.

Suppose you seal the container as before. Then you take the container and fly it out into space. Do you expect the pressure within the container to change?

Ravi Singh choudhary
jbriggs444 said:
Suppose you seal the container as before. Then you take the container and fly it out into space. Do you expect the pressure within the container to change?
You have a point. I got it; pressure will be same; that's how pressure is maintained in airplanes at high altitudes.

I think I am lacking in something very primitive concept. But now what I think let me tell you. When container was open; air above it also playing role in the pressure of the air inside the container; but when I put lid over it, I created a new wall for the collisions of the molecules inside the container that is compensating the less pressure due to no interaction with air outside the container.

## 1. Why does pressure not increase when I seal a container?

The pressure inside a sealed container remains constant because the amount of gas molecules and the volume of the container are both fixed. According to the ideal gas law, pressure is directly proportional to the number of gas molecules and the temperature, but inversely proportional to the volume. Therefore, if the volume is constant, the pressure will not increase.

## 2. Will the pressure increase if I seal a container with a gas inside?

No, the pressure inside the container will not increase as long as the temperature and volume remain constant. This is because the gas molecules are already exerting a certain amount of pressure on the walls of the container, and sealing the container does not change the number of molecules or the volume of the container.

## 3. Can pressure increase in a sealed container over time?

No, the pressure inside a sealed container will remain constant over time as long as the temperature and volume are constant. This is because the gas molecules will continue to collide with the walls of the container, maintaining a constant pressure.

## 4. What happens to the pressure inside a sealed container if I change the temperature?

If the temperature of a sealed container is changed, the pressure inside the container will also change. According to the ideal gas law, pressure is directly proportional to temperature. So, if the temperature increases, the pressure will also increase, and vice versa.

## 5. Can I change the pressure inside a sealed container by applying external force?

No, the pressure inside a sealed container cannot be changed by applying external force. This is because the walls of the container are rigid and do not allow for any changes in volume, which is necessary for pressure to change. However, if the container is not completely sealed, applying external force may cause the pressure to increase due to gas escaping from the container.