Real microstates change within mixing two gases

[sludger13]

Hello,
I'm looking for some changes of energy states of particles, as two gases are mixing together without total volume changing. That would explain increasing entropy better than their position combination.
I know the particle energy states are getting more closely (the band gaps are reducing) as the gas is expanding. Is this the same effect?
Thanks for every remark or advice.

 

[sludger13]

I think I found the answer - it is the same phenomenon like a gas expansion.

Dalton's Law that "each gas is a vacuum to the other gas"

Though I don't get it, why that band gap decreasing should happen during expansion.