### Theory:

The temperature at which the pressure and volume of a gas theoretically reach zero is called absolute zero.
Variation of pressure with temperature

At a temperature of $$–273.15$$ $$°C$$, the pressure extrapolates to zero for all gases.  It is called n as absolute zero or $$0$$ $$K$$. Some baseline temperatures in the three temperature scales are shown below.

 Temperature Kelvins($$K$$) Degree celcius($$°C$$) Degrees Fahrenheit($$°F$$) Boiling point of water $$373.1$$ $$100$$ $$212$$ Melting point of ice $$273.1$$ $$0$$ $$32$$ Absolute zero $$0$$ $$-273$$ $$460$$

We can convert the values from one unit to another unit by using the formula,

a) Convert $$30$$$$°C$$ to $$Kelvin$$

Solution:

$\begin{array}{l}{T}_{K}={T}_{\mathrm{°}C}+273.15\\ {T}_{K}=30+273.15\\ {T}_{K}=303.15\phantom{\rule{0.147em}{0ex}}K\end{array}$

b) Convert $$240$$ $$K$$ to $$°C$$

$\begin{array}{l}{T}_{\mathrm{°}C}={T}_{\mathrm{°}K}-273.15\\ {T}_{K}=240-273.15\\ {T}_{K}=-33.15\phantom{\rule{0.147em}{0ex}}K\end{array}$