The assumption that molecules collide with elasticity was postulated in the kinetic theory of gases. So my question is molecules should have higher tendency to collide obliquely and would therefore result in change of velocity (as the vector components would cancel or add up the velocities of molecules, resulting in change of velocities of molecules) and energy states of electron, are the assumptions not very correct or am I wrong?
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$\begingroup$ Causing an excitation (according to Bohr's theory at least) requires that the colliding atom have a minimum energy of ~10.2 eV. Most colliding atoms at and around room temperature have less energy. $\endgroup$– Aniruddha DebJan 12, 2020 at 3:45
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$\begingroup$ So, the assumption is not very strong? $\endgroup$– Shreya SoniJan 12, 2020 at 3:48
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$\begingroup$ But, are the collisions perfectly elastic? $\endgroup$– Shreya SoniJan 12, 2020 at 4:38
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$\begingroup$ Try to ask the above question as it is written eyes to eyes and watch, if the other person understands the question. As I bet the person will forget the beginning until you finish. As a guidance for scientific texts, it is adviced sencentes are 20-25 words long in average, with strong recommendation not to write ones longer than 35 words. Your single sentence has 64 words. $\endgroup$– PoutnikJan 12, 2020 at 6:54
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$\begingroup$ Could you clarify why you think your scenario shows that the process is not elastic? Elastic does not mean individual velocity can't change, it means there is no net loss in kinetic energy across all atoms. $\endgroup$– Karsten ♦Jan 13, 2020 at 15:12
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Inelastic collisions are such collisions, that dissipate mechanical energy to other energy forms. It may be e.g. acoustic energy, light, thermal energy ( in macro context only ) or internal energy of an object.
The change of the internal energy in molecular context can be creation/breaking of chemical bonds, or changes of electron energy states. In usual conditions of stable enough gases, these events are very negligible, as average kinetic energy is much smaller than the energy needed to such a change.
Be aware that even fully elastic collision generally leads to a change of the mechanical energy of an object, in whole, or its translational, vibrational and rotational parts.
Imagine 2 identical balls moving at the same speed on a colliding course. After the collision, they have still identical speed if and only if their collision was symmetric. Otherwise 1 ball will slow down and the other ball will speed up.
The justification of the kinetic gas theory is the best shown on very good agreement of prediction and observed behavior of permanent gasses at normal conditions.
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$\begingroup$ The postulate that a particular number of molecules posses a particular magnitude of velocities but oblique collisions should not result in such, if you could explain this keeping the above question in mind that will be great! $\endgroup$ Jan 12, 2020 at 15:32
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$\begingroup$ It is not very clear what you complain against, or disagree with. Even if by a magic wand all molecules got the same speed, in time shorter than a microsecond speed would get redistributed according Maxwell-Boltzmann distribution. $\endgroup$– PoutnikJan 12, 2020 at 17:22
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$\begingroup$ Speeds are constant, collisions are elastic. How can collisions and speeds be elastic and constant respectively? There is a higher probability of oblique collisions which should not result in the constant speed law. $\endgroup$ Jan 13, 2020 at 9:28
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$\begingroup$ Speeds are NOT constant. The speed of every gas molecule typically change 10 billion times per second, at each collision. What is constant is the speed distribution over the time at equilibrium. $\endgroup$– PoutnikJan 13, 2020 at 9:31
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