Why do gas laws use degree Kelvin rather than degree Celsius?
Kelvins are basically the same thing than Celsius, except you have to substract 273. 0 degree. Kelvin is -273 degree Celsius and it is the lowest temperature that can exist. Because all temperature values in Kelvin are positive, the calculations are easier to make and that is why Kelvins were created. Because gas temperatures are often below 0 degrees celsius, degree Kelvin is very handy.