Which factors can cause a change in the physical states of matter?

Fill in the blanks:
$(1)$ The properties of gases were first measured by ......... .
$(2)$ The dipole-dipole interaction energy between stationary polar molecules is proportional to .......... .
$(3)$ The interaction energy between rotating polar molecules is proportional to .......... .
$(4)$ The bond energy of a hydrogen bond is about ......... $kJ \ mol^{-1}$.

When the pressure of $1 \ mol$ of ammonia gas changes from $1 \ atm$ to $0.5 \ atm$ at constant temperature,the number of molecules will:

$A$ gaseous mixture contains $65\%$ $N_2$,$15\%$ $O_2$,and $20\%$ $CO_2$ by volume at a total pressure of $760 \, mm \, Hg$. Calculate the partial pressure of each gas in $mm \, Hg$.

Calculate the ratio of the effusion of $CO$ and $N_2$,when temperature and pressure gradients are held constant?

Gas $X$ diffuses three times faster than gas $Y$. What is the ratio of their densities,i.e.,$D_x : D_y$?