energygaspressurethermodynamics
Containers holding gas at a high pressure don't slowly lose the internal energy of the gas. It seems like the high speed particles would collide with the metal walls and slowly transfer their energy to the slower particles outside the container.
Even if the pressure is from more particles in the container, they can do work when released so they have energy. Shouldn't that energy dissipate over time?
As the comments to the question have stated, in real gasses ( contrasted to ideal gasses which just bounce around elastically) there exist both elastic and inelastic scatterings controlled by quantum mechanical interactions.
Photons are generated leading to what we call Black Body radiation and an isolated gas volume will lose energy according to the Stephan Boltzmann law.
the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time (also known as the black-body radiant exitance or emissive power), is directly proportional to the fourth power of the black body's thermodynamic temperature T:
Thus the gas does lose energy if the temperature of matter surrounding it is lower.
In answer to
I think another way to phrase this is, how do elastic collisions not lose any energy in the exchange
Elastic means an interaction of two particles where before and after , kinetic energy is conserved. If one assumes that only kinetic energies exist for this scatter ( as in the ideal gas) then energy is conserved because what one particle loses the other gains . If there are other forms of energy that can contribute to the two particle interaction then it is the total energy that is conserved. With billiard balls classically friction has to be taken into account with the energy balance, the same with the bouncing ball, and the kinetic energies stop being the total energy of the system. For particles in a gas it is the quantum mechanical framework, described above.
The pressure of a gas is defined as the force the gas would exert upon a surface or container. However, there is no need for a container for pressure to exist. For instance, the air you're breathing right now (unless you're in an airplane or submarine) has pressure due to the column of atmosphere above you. Stars are balls of gas (plasma, actually) that are pressurized by gravity; no containers to be seen.
Best Answer
Gases in containers at high pressures have those pressures because there are more molecules in them than in the same container at atmospheric pressure, not because there is a difference between the molecular energies. At the same temperature, two containers with different numbers of molecules in them have the same probability distribution of energies.
The pressure difference is owing to the difference between the collision frequencies with the walls in each case, the collision frequency being proportional to the number of molecules.
Question from OP
Firstly, it seems that you may be confusing temperature with concentration of energy (energy per volume). Temperature is wholly about the probability distribution of a system's particles, not about how much total energy there is. I'll try the following argument to try to show why it is temperature difference between the gas and its surroundings, and not the concentration of energy, that determines whether energy escapes through heat flow, which is the only way it can escape if the bottle is sealed.
Think of things from one particle's standpoint. From time to time it bumps into other gas particles, and also into the thermalized particles that make up the bottle walls. Sometimes these particles will have more energy than our lone particle, sometimes less. But, over the long term, the expected rate of transfer of energy from the particle is nought - that's what we mean, by definition, when we say that the system is at thermodynamic equilibrium. This zero expected rate depends wholly on the probability distributions of the system particle energies, it does not depend on how often the particles collide. If there were only one gas particle in the bottle (so you had a very hard vacuum), its mean kinetic energy would be set by the kinetic energies of the particles making the bottle wall up: it would reach a point where a collision with the wall were equally likely to lose or gain energy. And that expected energy would be the mean energy of the particles in the wall. Energy cannot simply come rushing in because it is more concentrated in the walls, the transfer is governed by stochastic, passive processes.