Why should Gay-Lussac's law be in Kelvins not in Celsius?

Answer 1

Gay-Lussac's Law is expressed:

P
-- = k
T

where k is a constant.

Let's say you use degrees Celsius. What happens when T = 0 (a fairly common occurrence!)?

If we use Kelvin, we don't have this problem in practice because zero degrees on the Kelvin scale is an extremely unlikely event. (ie, zero kinetic energy) Hope this is interesting to you.

Answer 2

Kelvin is on the scale which is easier to use because 0 is freezing.