Let's suppose we have temperatures 30°C and 35°C. Converting them to Kelvin we have 303.15K and 308.15K.
In the second case, the temperature difference is 5K. While in first case, temperature difference is 5°C, which is convertible to 278.15K.
This clearly is absurd. I have some ideas why it goes wrong, but could someone please provide a clear explanation? Cannot we use conversions on difference?
This seems to be a general problem with units which have additive relationship (Kelvin and Celsius) rather than a multiplicative one(metre -centimetres).