For gases, isothermal compressibility (k) is equal to

The change in entropy (∂S) for reversible process is

Efficiency of a Carnot engine working between hot reservoir at temperature T₁ and sink reservoir at temperature T^₂ is

Thermochemistry is the study of the relationship between Chemical energy and 

Specific heat at a constant pressure (C_p) is defined by

According of first law of thermodynamics the change in internal energy. (ΔE) accompanying a process, performing a work (W) and involving absorption of heat (Q) on the surroundings is given by the relation