Why do gas laws use degrees Kelvin rather than degrees Celsius?

1 Answer
Dec 22, 2015

Kelvin is an absolute scale, whereas Celsius is arbitrary.

What does this mean?

#"0 K"#, or #0# on the Kelvin scale, is absolute zero. This is the coldest matter can be, and also where the matter has #0# energy.

In order for gas laws to work, temperature has to be calculated on an absolute scale.

Celsius, on the other hand, has an arbitrary #0# degree point, which is the temperature when water melts.

Another problem with Celsius is that negative degrees are very possible, which may cause confusing results.

To extend this thought, other absolute temperature scales such as Rankine would work fine for gas laws. Fahrenheit, which is arbitrary, would not.