Why are liquids and gases categorised as fluids?

Calculate the partial pressure exerted by dioxygen from a mixture of $32 \ g$ $O_2$,$80 \ g$ $Ar$ (molar mass $40 \ g/mol$) and $4 \ g$ dihydrogen $(P_{\text{total}} = 10 \ bar)$. (in $bar$)

$x \ g$ of molecular oxygen $(O_2)$ is mixed with $200 \ g$ of neon $(Ne)$. The total pressure of the nonreactive mixture of $O_2$ and $Ne$ in the cylinder is $25 \ bar$. The partial pressure of $Ne$ is $20 \ bar$ at the same temperature and volume. The value of $x$ is $....$ [Given: Molar mass of $O_2 = 32 \ g \ mol^{-1}$. Molar mass of $Ne = 20 \ g \ mol^{-1}$]

The ratio of the partial pressure of a gaseous component to the total vapor pressure of the mixture is equal to .......

The rate of diffusion of $SO_2$,$CO_2$,$PCl_3$ and $SO_3$ are in the following order:

Provide the $SI$ units for the following gas properties:
$(i)$ Mass $(ii)$ Volume $(iii)$ Temperature $(iv)$ Pressure