If you are using the unit Kelvin, you are measuring the average KINETIC ENERGY OF MOLECULES.
Kelvin is the unit for measuring the absolute temperature of objects. Temperature refers to the degree of hotness or coldness of a body. The temperature of a body depends on the amount of heat that is applied to it, the amount of heat applied determine the value of kinetic energy that the particles of the body will possess; the higher the heat applied the higher the kinetic energy of the particles and vice versa.