1.2: The Molecular Interpretation of Entropy [Video]

As discussed previously, the second law of thermodynamics argues that all processes must increase the total entropy of the universe. However, the universe if often separated into the System and the Surroundings differing changes of entropy can be observed from a system level perspective. Many processes results in an increase in a system’s entropy (Delta S > 0):

• Increasing the volume that a gas can occupy will increase the disorder of a gas
• Dissolving a solute into a solution will increase the entropy of the solute – typically resulting in an increase in the entropy of the system. (Note: the solvation of a solute can sometimes result in a significant decrease in the solvent entropy – leading to a net decrease in entropy of the system)
• Phase changes from solid to liquid, or liquid to gas, lead to an increase in the entropy of the system

Some processes result in a decrease in …