Gases are kept in the air by their large kinetic energy

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Discussion Overview

The discussion revolves around the behavior of gases in the atmosphere, particularly focusing on the role of kinetic energy in keeping gas particles suspended in the air. Participants explore concepts related to particle motion, temperature effects, and the nature of gases compared to liquids.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that gases are kept in the air due to their large kinetic energy and questions whether a single particle would fall in a parabolic arc between collisions.
  • Another participant counters by emphasizing the density of air and the multitude of air particles, likening it to pouring water into water, suggesting that particles do not sink through their own medium.
  • A clarification is made regarding the role of collisions in keeping particles suspended, indicating that the discussion is focused on the motion of particles aside from collisions.
  • Participants discuss the reasons for colder temperatures at high altitudes, mentioning radiational cooling and the expansion of gases as they rise.
  • One participant introduces the concept that the average velocity of gas molecules is temperature-dependent, suggesting that high temperatures could allow molecules to exceed escape velocity, potentially leading to the loss of lighter gases like Hydrogen and Helium from the atmosphere.
  • A metaphor is proposed comparing air to a low-density liquid, with a participant sharing a personal reflection on observing cloud formations while flying, reinforcing the idea of air as a fluid medium.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of gas particles and the factors influencing their suspension in the atmosphere. There is no consensus on the implications of kinetic energy versus density or the reasons for temperature variations at altitude.

Contextual Notes

Some assumptions about particle behavior and temperature effects remain unaddressed, and the discussion does not resolve the complexities of gas dynamics or the interactions between temperature, density, and kinetic energy.

Who May Find This Useful

Individuals interested in atmospheric physics, gas behavior, and the conceptual understanding of particle dynamics may find this discussion relevant.

daveed
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gases are kept in the air by their large kinetic energy, no? if we observed one particle in the atmosphere, however, would we not observe it to fall in a parabolic arc(in between collisions, which keep it propped up) much as a macroscopic particle would?

this just gets me thinking because-with singular particles in a box, wouldn't the particle go towards the bottom of the box? or... if at that level the collision is elastic, it would go back to its original height , but there have the lowest kinetic energy

is that why its cold in high places?
 
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You neglected the fact that there are so many air particles(All kinds of mloecules) so that the "air particles" you mentioned would be in a medium of similar density. It's like pouring water into water; water does not sink through water like matter with high densities.
It's just that air has a very low density, so it doesn't seem that obvious.
 
i said "in between collisions, which keep it propped up". aside from the collisions.
 
daveed said:
is that why its cold in high places?

It's cold in high places for a couple of reasons. One is radiational cooling and another is that gases do work to expand as they climb thereby cooling.
 
Essentially yes, that is correct. But you cannot neglect the temperature. Since the average velocity of the molecules in a gas is determined by the temperature, if the temperature is high enough, the molecule may well have a velocity greater the escape velocity. So the parabolic path could take the molecule into space and free of the Earth's gravitational field. This is one reason why we do not have free Hydrogen or Helium in our atmosphere. The fact that H loves to react, will be another reason we do not find it. However even if it were not reactive any free H would be lost to space.

It is possible of fill an open container with a heavy gas, such as Ar or CO2.
 
I think kuenmao said it right:
Just think of air (gasses in general) as a low density liquid.

I had this feeling often when flying on a plane and watching the wonderous weird cloud formations, if you think of the air atmosphere as a liquid sea covering the whole earth, it doesn't look so weird anymore (yet beautiful anyway :-).
 

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