(N/A) Charles' law states that at constant pressure,the volume $(V)$ of a fixed mass of gas is directly proportional to its absolute temperature $(T)$: $V \propto T$ or $V = kT$.
It is observed that for all gases,the plot of volume versus temperature (in $^{\circ} C$) is a straight line. If this line is extrapolated to zero volume,it intersects the temperature axis at $-273^{\circ} C$.
Mathematically,if $V = V_0(1 + \frac{t}{273.15})$,then at $t = -273.15^{\circ} C$,the volume $V$ becomes zero.
Since a gas cannot have zero or negative volume,the temperature cannot go below $-273.15^{\circ} C$ (often rounded to $-273^{\circ} C$). In reality,all gases liquefy or solidify before reaching this temperature,making it the theoretical absolute zero.