At $27^{\circ} C$, $500 \ mL$ of helium diffuses in $30 \ minutes$. What is the time (in hours) taken for $1000 \ mL$ of $SO_2$ to diffuse under the same experimental conditions?

Match the following items in List-$I$ with the appropriate items in List-$II$:

List-$I$	List-$II$
$(A)$ Viscosity	$(I)$ Critical temperature
$(B)$ Ideal gas behaviour	$(II)$ Isobars
$(C)$ Liquefaction of gases	$(III)$ Compressibility factor
$(D)$ Charles' law	$(IV)$ $kg \ s^{-2}$
	$(V)$ $kg \ m^{-1} \ s^{-1}$

Assertion: Use of pressure cooker reduces cooking time.
Reason: At higher pressure,cooking occurs faster.

Identify the correct statements from the following:
$(A)$ The compressibility factor $(Z)$ for an ideal gas is $1$.
$(B)$ Uranium isotopes (${ }^{235}U$ and ${ }^{238}U$) are separated by converting them into $UF_6$ vapours.
$(C)$ Decrease in temperature increases the kinetic energy of gas molecules.

The density of a mixture of $He$ and $O_2$ gases at $27\,^{\circ}C$ and $760\, torr$ pressure is $0.543\, g\, dm^{-3}$. Calculate the percentage by mass of $He$ in the mixture.

Why does a sharp glass edge become smooth on heating it up to its melting point in a flame? Explain which property of liquids is responsible for this phenomenon.