# 4: The Second Law of Thermodynamics

- Page ID
- 41301

- 4.2: Entropy
- Entropy is a state function that is often erroneously referred to as the 'state of disorder' of a system. Qualitatively, entropy is simply a measure how much the energy of atoms and molecules become more spread out in a process and can be defined in terms of statistical probabilities of a system or in terms of the other thermodynamic quantities. Entropy is also the subject of the Second and Third laws of thermodynamics.

- 4.6: Gibbs Energy
- Gibbs energy is the energy of a chemical reaction that can be used to do non-mechanical work.