Summarizing Entropy and the Second Law of Thermodynamics

Summary

• Entropy is the loss of energy available to do work.
• Another form of the second law of thermodynamics states that the total entropy of a system either increases or remains constant; it never decreases.
• Entropy is zero in a reversible process; it increases in an irreversible process.
• The ultimate fate of the universe is likely to be thermodynamic equilibrium, where the universal temperature is constant and no energy is available to do work.
• Entropy is also associated with the tendency toward disorder in a closed system.

Glossary

entropy

a measurement of a system's disorder and its inability to do work in a system

change in entropy

the ratio of heat transfer to temperature \(Q/T\)

second law of thermodynamics stated in terms of entropy

the total entropy of a system either increases or remains constant; it never decreases