The ratio of rates of diffusion of helium $(He)$ to hydrogen $(H_2)$.

Air at sea level is dense. This is a practical application of

If some moles of $O_2$ diffuse in $18 \ sec$ and the same moles of another gas diffuse in $45 \ sec$,what is the molecular weight of the unknown gas?

Pressure cooker reduces cooking time for food because

Which shape does a liquid have in its lowest energy state?

Gaseous state is characterised by which of the following physical properties?
$I$. Gases mix evenly and completely in all proportions without any mechanical aid.
$II$. Gases exert pressure in all directions evenly.
$III$. Gases are highly compressible and have lower density than liquids and solids.
$IV$. The volume and shape of the gas is fixed.