Thermal analysis is a number of techniques in which the physical properties of a material are measured as a function of time, while the material is subjected to a controlled or programmed temperature change. Thermodynamics is the field of physics that underlies calorimetric investigations.
Thermodynamics is the study of the laws that govern the conversion of energy from one form to another, the direction in which heat will flow, and the availability of energy to do work. From the principles of thermodynamics one can derive general relations between such quantities as coefficients of expansion, compressibilities, specific heat capacities, heats of transformation, and magnetic and dielectric coefficients, especially as these are affected by temperature. The principles of thermodynamics also tell us which of these relations must be determined experimentally in order to completely specify all the properties of the system. The principal energy laws are derived from two famous laws of thermodynamics.
The second law, known as Carnot's principle, is defined by the concept of entropy (S), introduced by Clapeyron. The second law states that the quality of this energy is degraded irreversibly. Entropy characterises the degree of disorder in a system. As energy is transferred from one form to another, some is lost as heat. Entropy is merely the way to measure the energy that disperses or spreads out in a process (as a function of temperature). Entropy always either increases or remains constant in a closed system.
The change in entropy (DS) is equal to the heat transfer (DQ) divided by the temperature (T):
DS = (DQ) / T