# Summary

Thermodynamics deals with the study of flow of heat

Some important definitions of terms involved in thermodynamics:
• Enthalpy changes at constant pressure and volume are represented by H and U respectively. U is also known as the internal energy of the system.
• Intensive properties are the one which are independent of mass (temperature, density) and extensive properties are the one which depends upon the mass of the system under investigation (enthalpy, specific heat etc.)
• According to Hess's law of constant heat summation Enthalpy changes that occur in a system either at constant pressure (H) Or at constant volume (U) does not depend upon the path followed but depends only upon the initial and final states of the system.
• First law of thermodynamics states that "energy can neither be created nor destroyed but is somehow converted into useful work.
• Entropy of a system is defined as the degree of randomness Generally if S >0 then the process is said to be spontaneous
• An other important parameter that helps to get the knowledge of spontaneity criterion is the Gibbs free energy. For a spontaneous reaction always gibbs free energy change value (G) is always negative.