The three states of matter are the result of what?

If the density of a mixture of nitrogen and oxygen gases at $400 \ K$ and $1 \ atm$ pressure is $0.920 \ g \ L^{-1}$, what is the mole fraction of nitrogen in the mixture? ($R=0.082 \ L \ atm \ mol^{-1} \ K^{-1}$; assume ideal gas behavior for oxygen and nitrogen)

Two flasks of equal volume contain $O_2$ and $CH_3OH$ vapor respectively at $120\,^oC$ and $1.15\, atm$ pressure. Which of the following will be the same for both?

$0.5 \ mol$ each of $H_2, SO_2$ and $CH_4$ are present in a container. If a hole is made in the container,what will be the order of partial pressures of the gases remaining in the container after $3 \ hours$?

$A$ mixture of $He$ and $CH_4$ in a molar ratio of $4:1$ is present in a container at a pressure of $20 \ bar$. Due to a hole in the container,the gas mixture leaks out. What will be the composition of the gas mixture effusing out initially (in $: 1$)?

During the evaporation of a liquid,$..........$