(or 10): How does a vacuum work? Why does gaseous matter feel pressured (pardon pun) to occupy as much space in a vacuum as possible?

Question

Reading The Martian and thinking about things like depressurisation – why does air from a higher concentration feel the need to rush through a small leak with enough force to rip or blow things apart instead of staying put?

What calls it from the vacuum for it to be so obsessed in doing so?

In: Planetary Science

Answer 1

>why does air from a higher concentration feel the need to rush through a small leak with enough force to rip or blow things apart instead of staying put

2 main points here.

1. In gas form, the molecules are moving quite freely, flying about in all directions bouncing off the walls of the container. Relatively similar pressures inside the container and outside? The forces imparted on the container by all these collisions are relatively in balance. Dial up the pressure? Now there are either more collisions occurring on the higher pressure side, or collisions imparting more energy (or both). This translates to the macroscopic scale as a force on the walls of the container. More pressure difference, more force imbalance.

2. The container has some properties based on its shape, materials, quality of materials, etc. The combination of these properties determines the container’s ability to withstand forces. If the pressure difference is cranked-up high enough the forces overcome the containers ability to hold its shape, and it starts to deform. Typically this deformation weakens the container further, so a catastrophic failure occurs (boom). Same goes for introduction of a small hole (leak).

Regarding why the air doesn’t just stay put… we call that a solid. Technically we could cool air far enough for it to solidify (and just stay put), but it doesn’t do us any good for breathing at that point.

If you want to know why molecules move more freely in a gas vs liquid vs solid, it becomes a discussion of the balance of kinetic energy vs intermolecular forces, but that seems to be getting out of the scope of your question. Phases of matter or phase change would be searches of you want to dive into the rabbit hole.