Here's why:

* Absolute Zero: The Kelvin scale starts at absolute zero (-273.15°C), which is the theoretical point where all molecular motion ceases. This is important because the ideal gas law assumes that gas molecules have no volume and do not interact with each other.

* Direct Proportionality: In the ideal gas law, pressure and volume are directly proportional to temperature. This relationship only holds true when using an absolute temperature scale like Kelvin.

* Simplicity: Using Kelvin eliminates the need for constant adjustments or conversions when dealing with gas law calculations.

Here's the ideal gas equation:

PV = nRT

Where:

* P = Pressure

* V = Volume

* n = Number of moles of gas

* R = Ideal gas constant

* T = Temperature (in Kelvin)