In thermodynamics, the Kelvin (K) scale is often used instead of the Celsius (°C) scale when working with temperature differences or absolute temperatures. The Kelvin scale is an absolute temperature scale, meaning that it starts from absolute zero, the point at which all molecular motion ceases. On the Kelvin scale, temperature intervals and differences are the same as on the Celsius scale, but the numerical values are shifted.
The Kelvin scale is preferred in thermodynamics because it simplifies calculations and eliminates the need for negative temperature values, which can be problematic in certain equations and formulas. Additionally, many fundamental thermodynamic laws, such as the ideal gas law and the laws of thermodynamics, are stated using the Kelvin scale.
To convert temperature values from Celsius to Kelvin, you simply need to add 273.15 to the Celsius temperature. This conversion accounts for the shift in numerical values between the two scales, while keeping the temperature differences consistent. So, if the initial temperature is given in Celsius (e.g., 40°C), you can convert it to Kelvin by adding 273.15, resulting in 313.15 K.
By using Kelvin, which is an absolute temperature scale, thermodynamic calculations become more accurate and convenient since it aligns with the fundamental principles and equations used in the field.