Question

When using Charles's law, why should the temperature units always be kelvin?

Answer 1

Theoretically, a gas can never reach zero or a negative temp and always gives positive numbers

*Hope this helps

Answer 2

Explanation:

On the basis of Charle's law, the volume of a given gas mass changes straightforwardly with the absolute temperature of the gas when the pressure is maintained the same. The absolute temperature is determined with the Kelvin scale. There is a need to use the Kelvin scale as zero on the Kelvin scale relates to a complete stoppage of molecular movement.  

In the gas law problems, the Kelvin scale is used as the volume and pressure of a gas relies upon the motion or kinetic energy of the particles. The Kelvin scale is equivalent to the kinetic energy of the particles, that is, 0 Kelvin signifies 0 kinetic energy, and on the other hand, 0 degree Celsius is basically the freezing point of water.