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Collapsing molecules

Question: What happens to air molecules that enables them to withstand massive pressures and avoid collapsing to zero volume?


A few points to think about:
Molecules of air (in a gaseous form) are widely separated.
The forces on them are not constant but only occur for very short time during collisions between each other or the walls of the container.
Liquids are virtually incompressible and you can't solidify a liquid by pressure alone. The kinetic energy of the molecules will "keep them apart".
Try and find out about the Pauli exclusion principle there are only certain allowed energy levels within an atom or molecule.

What is a molecule of air there is actually no such thing. Air is a mixture of gases, oxygen (diatomic), nitrogen (diatomic) and a pretty small proportional of other gases mostly monatomic. The diatomic molecule will not bend to take up a smaller volume although the vibrations may reduce at high pressure.

Now for some explanation.
A gas withstands the pressure exerted on it because the molecules of the gas collide with the walls of the container. Nothing happens to the size, shape and speed of molecules as the pressure is increased. If the pressure is doubled the volume of the gas is halved and obviously as a result of this the molecules hit the walls of the container more often.

Because the speed of the molecules stays the same the force ON each molecule at a collision does not change no matter what the pressure is. It only changes if the temperature of the gas changes.

The size and shape of the molecule is kept the same by the electromagnetic forces within the molecule. In the same way that a bed spring returns to its original size and shape when someone gets off a bed so the molecule returns to its natural size and shape after a collision.

Eventually under high pressure the air will turn into a liquid (if the temperature is low enough). As I have said, liquids are virtually incompressible. The electrostatic force between the electron clouds of the atoms resists them being forced together. The size of this force increases as the distance between the atoms gets less.
© Keith Gibbs 2007